@article{muñoz-carpena_carmona-cabrero_yu_fox_batelaan_2023, title={Convergence of mechanistic modeling and artificial intelligence in hydrologic science and engineering}, url={https://doi.org/10.1371/journal.pwat.0000059}, DOI={10.1371/journal.pwat.0000059}, abstractNote={Hydrology is a mature physical science based on application of first principles. However, the water system is complex and its study requires analysis of increasingly large data available from conventional and novel remote sensing and IoT sensor technologies. New data-driven approaches like Artificial Intelligence (AI) and Machine Learning (ML) are attracting much “hype” despite their apparent limitations (transparency, interpretability, ethics). Some AI/ML applications lack in addressing explicitly important hydrological questions, focusing mainly on “black-box” prediction without providing mechanistic insights. We present a typology of four main types of hydrological problems based on their dominant space and time scales, review their current tools and challenges, and identify important opportunities for AI/ML in hydrology around three main topics: data management, insights and knowledge extraction, and modelling structure. Instead of just for prediction, we propose that AI/ML can be a powerful inductive and exploratory dimension-reduction tool within the rich hydrological toolchest to support the development of new theories that address standing gaps in changing hydrological systems. AI/ML can incorporate other forms of structured and non-structured data and traditional knowledge typically not considered in process-based models. This can help us further advance process-based understanding, forecasting and management of hydrological systems, particularly at larger integrated system scales with big models. We call for reimagining the original definition of AI in hydrology to incorporate not only today’s main focus on learning, but on decision analytics and action rules, and on development of autonomous machines in a continuous cycle of learning and refinement in the context of strong ethical, legal, social, and economic constrains. For this, transdisciplinary communities of knowledge and practice will need to be forged with strong investment from the public sector and private engagement to protect water as a common good under accelerated demand and environmental change.}, journal={PLOS Water}, author={Muñoz-Carpena, Rafael and Carmona-Cabrero, Alvaro and Yu, Ziwen and Fox, Garey and Batelaan, Okke}, editor={Madramootoo, Chandra A.Editor}, year={2023}, month={Aug} }
 @article{chen_carley_munoz-carpena_ferruzzi_yuan_henry_blankinship_veith_breckels_fox_et al._2023, title={Incorporating the benefits of vegetative filter strips into risk assessment and risk management of pesticides}, volume={9}, ISSN={["1551-3793"]}, url={https://doi.org/10.1002/ieam.4824}, DOI={10.1002/ieam.4824}, abstractNote={Abstract}, journal={INTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT}, author={Chen, Huajin and Carley, Danesha Seth and Munoz-Carpena, Rafael and Ferruzzi, Giulio and Yuan, Yongping and Henry, Eric and Blankinship, Amy and Veith, Tamie L. and Breckels, Ross and Fox, Garey and et al.}, year={2023}, month={Sep} }
 @article{kassa_castro-bolinaga_guertault_fox_russell_brown_2023, title={Quantifying the Impact of Model Selection When Examining Bank Retreat and Sediment Transport in Stream Restoration}, volume={15}, ISSN={["2073-4441"]}, url={https://doi.org/10.3390/w15081448}, DOI={10.3390/w15081448}, abstractNote={The objective of this study was to assess the performance of form-based and process-based models, and of local-scale and reach-scale models, used to examine bank retreat and sediment transport in stream restoration. The evaluated models were the Bank Erosion Hazard Index (BEHI), Bank Assessment for Nonpoint Source Consequences of Sediment (BANCS), Bank Stability and Toe Erosion Model (BSTEM), and HEC River Analysis System (HEC-RAS 1D). Model-to-model assessments were conducted to quantify the impact of model selection when predicting applied stress and geomorphic change in a restored stream in North Carolina, USA. Results indicated that the mobility of the bed dictated model selection at the reach-scale. The process-based HEC-RAS 1D was needed to accurately analyze the sand-bed stream, predicting amounts of geomorphic change comparable to measured data and up to three orders of magnitude higher than those from local-scale models. At the local-scale, results indicated that the bank retreat mechanism and flow variability constrained model selection. The form-based BEHI and BANCS did not directly account for geotechnical failure nor capture severe floods, underpredicting amounts of geomorphic change by an order of magnitude when compared to the process-based BSTEM, and failing to characterize erosion potential and applied stresses after short-term morphodynamic adjustments.}, number={8}, journal={WATER}, author={Kassa, Kayla and Castro-Bolinaga, Celso and Guertault, Lucie and Fox, Garey A. A. and Russell, Periann and Brown, Emily D. D.}, year={2023}, month={Apr} }
 @article{margenot_zhou_mcdowell_hebert_fox_schilling_richmond_kovar_wickramarathne_lemke_et al._2023, title={Streambank erosion and phosphorus loading to surface waters: Knowns, unknowns, and implications for nutrient loss reduction research and policy}, volume={52}, ISSN={["1537-2537"]}, DOI={10.1002/jeq2.20514}, abstractNote={Abstract}, number={6}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Margenot, Andrew J. and Zhou, Shengnan and Mcdowell, Richard and Hebert, Thomas and Fox, Garey and Schilling, Keith and Richmond, Shawn and Kovar, John L. and Wickramarathne, Niranga and Lemke, Dean and et al.}, year={2023}, month={Nov}, pages={1063–1079} }
 @article{fox_guertault_castro-bolinaga_swanson_2022, title={GUIDANCE ON APPLIED PRESSURE HEADS FOR QUANTIFYING COHESIVE SOIL ERODIBILITY WITH A JET EROSION TEST (JET)}, volume={65}, ISSN={["2769-3287"]}, DOI={10.13031/ja.14884}, abstractNote={
						Highlights
					}, number={6}, journal={JOURNAL OF THE ASABE}, author={Fox, Garey A. and Guertault, Lucie and Castro-Bolinaga, Celso and Swanson, Alexis}, year={2022}, pages={1443–1450} }
 @article{fox_guertault_castro-bolinaga_allen_bigham_bonelli_hunt_kassa_langendoen_porter_et al._2022, title={PERSPECTIVE: LESSONS LEARNED, CHALLENGES, AND OPPORTUNITIES IN QUANTIFYING COHESIVE SOIL ERODIBILITY WITH THE JET EROSION TEST (JET)}, volume={65}, ISSN={["2769-3287"]}, url={http://dx.doi.org/10.13031/ja.14714}, DOI={10.13031/ja.14714}, abstractNote={Highlights}, number={2}, journal={JOURNAL OF THE ASABE}, author={Fox, Garey A. and Guertault, Lucie and Castro-Bolinaga, Celso and Allen, Peter and Bigham, Kari A. and Bonelli, Stephane and Hunt, Sherry Lynn and Kassa, Kayla and Langendoen, Eddy J. and Porter, Erin and et al.}, year={2022}, pages={197–207} }
 @article{fox_munoz-carpena_brooks_hall_2021, title={ADVANCING SURFACE WATER PESTICIDE EXPOSURE ASSESSMENTS FOR ECOSYSTEM PROTECTION}, volume={64}, ISSN={["2151-0040"]}, DOI={10.13031/trans.14225}, abstractNote={Highlights}, number={2}, journal={TRANSACTIONS OF THE ASABE}, author={Fox, G. A. and Munoz-Carpena, R. and Brooks, B. and Hall, T.}, year={2021}, pages={377–387} }
 @article{munoz-carpena_lauvernet_carluer_fox_2021, title={Comment on "Modeling slope rainfall-infiltration-runoff process with shallow water table during complex rainfall patterns" by Wu et al. (2021)}, volume={13}, ISSN={["2589-9155"]}, DOI={10.1016/j.hydroa.2021.100113}, abstractNote={In this comment we draw attention to parametrization errors in this recently published article when comparing an existing model for soil infiltration under shallow water conditions, SWINGO, with an alternative solution and Richards benchmark solution. After correcting the errors, a new model comparison shows SWINGO ability to match the other approaches and supports the general validity of SWINGO’s simplified approach against the more complicated solutions.}, journal={JOURNAL OF HYDROLOGY X}, author={Munoz-Carpena, R. and Lauvernet, C. and Carluer, N. and Fox, G. A.}, year={2021}, month={Dec} }
 @article{halihan_hager_guertault_fox_2021, title={DETECTING MACROPORE FINGERING USING TEMPORAL ELECTRICAL RESISTIVITY IMAGING}, volume={37}, ISSN={["1943-7838"]}, DOI={10.13031/aea.14294}, abstractNote={Highlights}, number={5}, journal={APPLIED ENGINEERING IN AGRICULTURE}, author={Halihan, Todd and Hager, John P. and Guertault, Lucie and Fox, Garey A.}, year={2021}, pages={861–870} }
 @article{orozco-lopez_munoz-carpena_gao_fox_2021, title={HIGH-RESOLUTION PORE-SCALE WATER CONTENT MEASUREMENT IN A TRANSLUCENT SOIL PROFILE FROM LIGHT TRANSMISSION}, volume={64}, ISSN={["2151-0040"]}, DOI={10.13031/trans.14292}, abstractNote={Highlights}, number={3}, journal={TRANSACTIONS OF THE ASABE}, author={Orozco-Lopez, E. and Munoz-Carpena, R. and Gao, B. and Fox, G.}, year={2021}, pages={949–962} }
 @article{fox_fox_guertault_2020, title={A CASE STUDY ON THE RELEVANCE OF THE JOURNAL IMPACT FACTOR}, volume={63}, ISSN={["2151-0040"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85085130127&partnerID=MN8TOARS}, DOI={10.13031/trans.13756}, abstractNote={Highlights}, number={2}, journal={TRANSACTIONS OF THE ASABE}, author={Fox, G. A. and Fox, A. K. and Guertault, L.}, year={2020}, pages={243–249} }
 @article{wilson_ursic_fox_nieber_2020, title={Internal erosion of soil pipes: Sediment rating curves for soil pipes}, url={https://doi.org/10.1002/esp.5009}, DOI={10.1002/esp.5009}, abstractNote={Abstract}, journal={Earth Surface Processes and Landforms}, author={Wilson, G.V. and Ursic, M. and Fox, G.A. and Nieber, John L.}, year={2020}, month={Dec} }
 @article{guertault_fox_2020, title={Performance of preferential flow models in predicting infiltration through a remolded soil with artificial macropores}, volume={19}, ISSN={["1539-1663"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85097260363&partnerID=MN8TOARS}, DOI={10.1002/vzj2.20055}, abstractNote={Abstract}, number={1}, journal={VADOSE ZONE JOURNAL}, author={Guertault, Lucie and Fox, Garey A.}, year={2020} }
 @article{hester_fox_2020, title={Preferential Flow in Riparian Groundwater: Gateways for Watershed Solute Transport and Implications for Water Quality Management}, volume={56}, url={https://doi.org/10.1029/2020WR028186}, DOI={10.1029/2020WR028186}, abstractNote={Abstract}, number={12}, journal={Water Resources Research}, publisher={American Geophysical Union (AGU)}, author={Hester, Erich T. and Fox, Garey A.}, year={2020}, month={Dec} }
 @article{khanal_fox_guertault_2020, title={SOIL MOISTURE IMPACTS LINEAR AND NONLINEAR ERODIBILITY PARAMETERS FROM JET EROSION TESTS}, volume={63}, ISSN={["2151-0040"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85090917985&partnerID=MN8TOARS}, DOI={10.13031/trans.13835}, abstractNote={Highlights}, number={4}, journal={TRANSACTIONS OF THE ASABE}, author={Khanal, A. and Fox, G. A. and Guertault, L.}, year={2020}, pages={1123–1131} }
 @article{muñoz-carpena_ritter_fox_2019, title={Comparison of empirical and mechanistic equations for vegetative filter strip pesticide mitigation in long-term environmental exposure assessments}, volume={165}, ISSN={0043-1354}, url={http://dx.doi.org/10.1016/j.watres.2019.114983}, DOI={10.1016/j.watres.2019.114983}, abstractNote={Recent advances in mechanistic modeling of vegetated filter strips (VFS) have made it possible to incorporate VFS mitigation into environmental exposure assessments (EEAs). However, outside of fixed efficiency approaches, there are no widely adopted and standardized procedures for incorporating VFS quantitative mitigation into long-term, higher-tier EEAs. A source of hesitation involves the use of empirical equations for predicting pesticide trapping by the VFS. A recent study evaluated existing empirical equations and a mechanistic mass-balance approach using the most extensive field database available of VFS pesticide efficiency from single-event storms. That study concluded that an updated empirical equation (Sabbagh equation) and a mechanistic mass-balance approach performed reasonably well. The objective of this research was to study the effect of upscaling the VFS trapping equations from single events into long-term EEAs. The U.S. EPA Pesticide in Water Calculator (PWC) model linked with the Vegetative Filter Strip MODeling system (VFSMOD) long-term EEA modeling framework (30 yr) was updated to incorporate the alternative trapping equations and tested VFS mitigation results under contrasting agroecological settings with varying erosion/sediment transport conditions. Differences in both acute and chronic 90th percentile estimated environmental exposure concentrations (EECs) were relatively small when comparing predictions using the four pesticide trapping equations. A global sensitivity analysis (GSA) also indicated that selection of a specific trapping equation for predicting EECs was less important than other important input factors such as the VFS length and pesticide properties. However, in terms of the percent reductions in EECs, the choice of pesticide trapping equation was as important as the VFS length. This research builds upon the conclusion of previous single-event studies that the mechanistic mass-balance and refit Sabbagh empirical equation were both valid for EEAs. The mass balance approach represents a reasonable option for regulatory agencies that prefer mechanistic approaches.}, journal={Water Research}, publisher={Elsevier BV}, author={Muñoz-Carpena, Rafael and Ritter, Amy and Fox, Garey A.}, year={2019}, month={Nov}, pages={114983} }
 @article{halihan_miller_correll_heeren_fox_2019, title={Field Evidence of a Natural Capillary Barrier in a Gravel Alluvial Aquifer}, volume={18}, ISSN={1539-1663}, url={http://dx.doi.org/10.2136/vzj2018.01.0008}, DOI={10.2136/vzj2018.01.0008}, abstractNote={Core Ideas
A tracer test in a gravel aquifer detected a natural capillary barrier.
Electrical resistivity data combined with well data found two separate vadose zone flow paths.
Phosphorus transport is limited, as it needs to migrate through soil before gravel.
Ozark streams commonly feature “composite” floodplains, in which the vadose zone consists of silt or silt loam soils (∼1 m thick) overlying gravel subsoil. Previous work has shown that preferential flow paths can exist within the gravel subsoil, which can conduct water and P at rates exceeding the sorption capacity of the gravel. At a site on Barren Fork Creek, a 1‐ by 1‐m infiltration plot was constructed and an infiltration experiment was performed using sequentially introduced solutes including P (the constituent of regulatory interest), Rhodamine‐WT (Rh‐WT, a visual tracer), and Cl− (an electrical tracer). The solute transport was measured with monitoring wells (MWs) placed 1 m from the plot boundary and 5 m down the groundwater flow gradient using an electrical resistivity imaging (ERI) array. The ERI method utilized differences between a pre‐infiltration background image and subsequent temporal images taken during the test to quantify changes induced by the tracers. The infiltration test maintained a steady‐state flow rate of 4.5 L min−1 for 84.75 h. Electrical resistivity imaging data showed significant changes in resistivity induced by the tracers within the soil vadose zone under the plot but no similar changes within the gravel, indicating that the interface was acting as a capillary barrier. Electrical resistivity images 5 m away from the plot showed tracer breakthrough into the gravel in areas not sampled by the MWs. Solute detection was limited in MWs, indicating that MWs could not adequately monitor movement below the capillary barrier because it controlled migration of solute to the heterogeneous phreatic zone.}, number={1}, journal={Vadose Zone Journal}, publisher={Wiley}, author={Halihan, Todd and Miller, Ronald B. and Correll, David and Heeren, Derek M. and Fox, Garey A.}, year={2019}, pages={180008} }
 @article{wanger_wanger_fox_wilson_nieber_fox_wilson_nieber_2019, title={Laboratory Experiments on the Removal of Soil Plugs During Soil Piping and Internal Erosion}, volume={62}, ISSN={2151-0040}, url={http://dx.doi.org/10.13031/trans.13092}, DOI={10.13031/trans.13092}, abstractNote={Abstract.}, number={1}, journal={Transactions of the ASABE}, publisher={American Society of Agricultural and Biological Engineers (ASABE)}, author={Wanger, Mikayla and Wanger, Mikayla and Fox, Garey A. and Wilson, Glenn V. and Nieber, John and Fox, Garey A. and Wilson, Glenn V. and Nieber, John}, year={2019}, pages={83–93} }
 @article{nieber_wilson_fox_2019, title={Modeling Internal Erosion Processes in Soil Pipes: Capturing Geometry Dynamics}, volume={18}, ISSN={1539-1663}, url={http://dx.doi.org/10.2136/vzj2018.09.0175}, DOI={10.2136/vzj2018.09.0175}, abstractNote={Core Ideas
Soil pipes are important features contributing to nonuniform flow in the vadose zone.
Soil pipe flow and internal erosion is modeled with coupled flow and transport equations.
Modeling results compare favorably to experimental measurements.
The flow of water in a soil pipe and the resulting erosion of the soil pipe wall is simulated using a numerical solution of the Reynolds‐averaged Navier–Stokes equations coupled with the well‐known linear excess shear stress equation and the governing equation for transport of suspended sediment in turbulent flow. The modeling results are compared with an experiment in which the entrance to the soil pipe constructed in a laboratory flume was subjected to a constant head of water in a reservoir. The modeled pipe discharge was in good agreement with the measured results when roughness was imposed on the pipe wall. The temporal growth of the soil pipe was in good agreement with the experimental results when using a soil erodibility coefficient of 0.0025 s/m. Several assumptions were made in model formulation, the most significant being that the soil pipe grows uniformly along its length and that no sediment deposition occurs. Recommendations for future work regarding these assumptions as well as others are discussed.}, number={1}, journal={Vadose Zone Journal}, publisher={Wiley}, author={Nieber, J.L. and Wilson, G.V. and Fox, G.A.}, year={2019}, pages={0} }
 @article{fox_douglas-mankin_muthukumarappan_zhu_walker_2019, title={Navigating the Publication Process: An ASABE Journals’ Perspective}, volume={62}, ISSN={2151-0040}, url={http://dx.doi.org/10.13031/trans.13648}, DOI={10.13031/trans.13648}, abstractNote={Abstract.  Highlights}, number={5}, journal={Transactions of the ASABE}, publisher={American Society of Agricultural and Biological Engineers (ASABE)}, author={Fox, Garey A. and Douglas-Mankin, Kyle R. and Muthukumarappan, Kasiviswanathan and Zhu, Jun and Walker, Joseph C.}, year={2019}, pages={1147–1153} }
 @article{fox_2019, title={Process-Based Design Strengthens the Analysis of Stream and Floodplain Systems under a Changing Climate}, volume={62}, ISSN={2151-0040}, url={http://dx.doi.org/10.13031/trans.13594}, DOI={10.13031/trans.13594}, number={6}, journal={Transactions of the ASABE}, publisher={American Society of Agricultural and Biological Engineers (ASABE)}, author={Fox, Garey  A.}, year={2019}, pages={1735–1742} }
 @article{nelson_montefiore_anthony_merriman_kuster_fox_2019, title={Undergraduate Perceptions of Climate Education Exposure in Natural Resources Management}, volume={62}, ISSN={2151-0040}, url={http://dx.doi.org/10.13031/trans.13361}, DOI={10.13031/trans.13361}, abstractNote={Abstract. To meet rising demands for climate-literate workers, undergraduate courses and curricula will require updates so that students are afforded opportunities to engage in climate science education. Previous research on undergraduate climate education has primarily focused on evaluating whether students have grounding in essential climate science principles, but these studies fail to capture the degree to which students feel they are exposed to climate education in their undergraduate programs and courses. In this study, we characterize recent trends in undergraduates’ perceived exposure to climate education across the U.S. by analyzing responses to a national survey of graduate students who attended undergraduate institutions in the U.S. (n = 423). Survey respondents scored the levels of exposure that they received to a variety of climatological topics during their undergraduate studies, which ranged from applied (e.g., earth observations, numerical modeling) to interdisciplinary (e.g., agricultural climatology, hydroclimatology) and specialized (e.g., boundary-layer climatology). Our results reveal that those who received bachelor’s degrees from programs related to human dimensions of natural resources management (e.g., geography, resource economics) generally felt that their undergraduate curricula provided them with exposure to climate education, whereas those who graduated from programs in engineering and the agricultural and life sciences largely reported a lack of climate coverage in their undergraduate studies. Students of all disciplinary backgrounds indicated that they received poor exposure to numerical modeling of historical and future climatic conditions. Findings from this study underline key areas in which curricular or course improvements are needed to ensure that future decision-makers are confident in their practical use of climate science. Keywords: Climate change, Climate science, Natural resources management, Postsecondary education, Undergraduate education, United States.}, number={3}, journal={Transactions of the ASABE}, publisher={American Society of Agricultural and Biological Engineers (ASABE)}, author={Nelson, Natalie G. and Montefiore, Lise and Anthony, Cord and Merriman, Laura and Kuster, Emma and Fox, Garey A.}, year={2019}, pages={831–839} }
 @article{enlow_fox_boyer_stoecker_storm_starks_guertault_2018, title={A modeling framework for evaluating streambank stabilization practices for reach-scale sediment reduction}, volume={100}, ISSN={1364-8152}, url={http://dx.doi.org/10.1016/j.envsoft.2017.11.010}, DOI={10.1016/j.envsoft.2017.11.010}, abstractNote={Process-based models can predict stream response to streambank stabilization. However, a framework does not exist on how to explicitly utilize these models to evaluate stabilization measures prior to implementation. This research developed a framework to evaluate stabilization practices using hydraulic and sediment transport models, landowner preferences, construction costs, and effectiveness. This framework produces sediment reduction graphs to determine the stabilization length as well as cost graphs. The methodology was applied to Fivemile Creek in western Oklahoma. A CONCEPTS simulation was developed for a 10.25-km reach and several stabilization techniques (grade control, riprap toe, and vegetation) were simulated. Incorporating multiple stabilization practices simultaneously resulted in higher sediment loads, but also higher costs which were quantifiable using the framework. Vegetation with 2:1 bank slopes was the most cost-effective stabilization technique. With that said, the framework provided a process-based understanding of the system that also highlighted the need for grade control for long-term effectiveness.}, journal={Environmental Modelling & Software}, publisher={Elsevier BV}, author={Enlow, Holly K. and Fox, Garey A. and Boyer, Tracy A. and Stoecker, Art and Storm, Daniel E. and Starks, Patrick and Guertault, Lucie}, year={2018}, month={Feb}, pages={201–212} }
 @article{akay_özer_fox_wilson_2018, title={Application of fibrous streambank protection against groundwater seepage erosion}, volume={565}, ISSN={0022-1694}, url={http://dx.doi.org/10.1016/j.jhydrol.2018.08.010}, DOI={10.1016/j.jhydrol.2018.08.010}, abstractNote={Groundwater flow is one of the main driving factors in the erosion of streambanks, particularly during return flow of bank storage as sediment particles on the bank face may be entrapped or liquefied by seepage flow into the stream, and when acting in concert with fluvial forces. Previous research has mainly focused on seepage erosion mechanisms, whereas in this study, a remedial solution using randomly distributed 6-mm-long polypropylene fibers mimicking the behavior of plant roots in slopes was investigated by laboratory physical streambank model experiments. Reduced-scale sandy (14 kN/m3 unit weight) streambank models (45° bank slope) with dimensions of 195 cm long, 100 cm wide and 110 cm high were constructed in an erosion flume. Two different seepage gradients were generated within the streambanks by maintaining piezometric heads of 50 cm-H2O and 100 cm-H2O in the upstream section of the erosion flume during experiments. Models were equipped with vibrating wire piezometers to measure the pore-water pressures within the streambank. In addition, tensiometers measured pore-water pressures near the wall section. Erosion of sediment from the streambank initiated concurrently as seepage flow emerged on the bare streambank surface. Erosion volumes were computed by three-dimensional laser scanning. Triaxial compression tests on sand samples (fiber gravimetric content ranged from 0% to 1.0%) indicated an increase in cohesion by fiber content. Fibrous streambank protection with 0.3% fiber content inclusion reduced the total amount of seepage erosion by 35%, and 47% under 50-, and 100 cm-H2O piezometric head boundary condition (BC), respectively. Seepage erosion rate and seepage discharge demonstrated a power-law relationship. Due to the increased cohesion, fibrous streambank protection with 1.0% fiber content effectively prevented seepage erosion during streambank experiments under the same BCs.}, journal={Journal of Hydrology}, publisher={Elsevier BV}, author={Akay, Onur and Özer, A. Tolga and Fox, Garey A. and Wilson, Glenn V.}, year={2018}, month={Oct}, pages={27–38} }
 @article{fox_muñoz-carpena_purvis_2018, title={Controlled laboratory experiments and modeling of vegetative filter strips with shallow water tables}, volume={556}, ISSN={0022-1694}, url={http://dx.doi.org/10.1016/j.jhydrol.2017.10.069}, DOI={10.1016/j.jhydrol.2017.10.069}, abstractNote={Natural or planted vegetation at the edge of fields or adjacent to streams, also known as vegetative filter strips (VFS), are commonly used as an environmental mitigation practice for runoff pollution and agrochemical spray drift. The VFS position in lowlands near water bodies often implies the presence of a seasonal shallow water table (WT). In spite of its potential importance, there is limited experimental work that systematically studies the effect of shallow WTs on VFS efficacy. Previous research recently coupled a new physically based algorithm describing infiltration into soils bounded by a water table into the VFS numerical overland flow and transport model, VFSMOD, to simulate VFS dynamics under shallow WT conditions. In this study, we tested the performance of the model against laboratory mesoscale data under controlled conditions. A laboratory soil box (1.0 m wide, 2.0 m long, and 0.7 m deep) was used to simulate a VFS and quantify the influence of shallow WTs on runoff. Experiments included planted Bermuda grass on repacked silt loam and sandy loam soils. A series of experiments were performed including a free drainage case (no WT) and a static shallow water table (0.3–0.4 m below ground surface). For each soil type, this research first calibrated VFSMOD to the observed outflow hydrograph for the free drainage experiments to parameterize the soil hydraulic and vegetation parameters, and then evaluated the model based on outflow hydrographs for the shallow WT experiments. This research used several statistical metrics and a new approach based on hypothesis testing of the Nash-Sutcliffe model efficiency coefficient (NSE) to evaluate model performance. The new VFSMOD routines successfully simulated the outflow hydrographs under both free drainage and shallow WT conditions. Statistical metrics considered the model performance valid with greater than 99.5% probability across all scenarios. This research also simulated the shallow water table experiments with both free drainage and various water table depths to quantify the effect of assuming the former boundary condition. For these two soil types, shallow WTs within 1.0–1.2 m below the soil surface influenced infiltration. Existing models will suggest a more protective vegetative filter strip than what actually exists if shallow water table conditions are not considered.}, journal={Journal of Hydrology}, publisher={Elsevier BV}, author={Fox, Garey A. and Muñoz-Carpena, Rafael and Purvis, Rebecca A.}, year={2018}, month={Jan}, pages={1–9} }
 @article{muñoz-carpena_fox_ritter_perez-ovilla_rodea-palomares_2018, title={Effect of vegetative filter strip pesticide residue degradation assumptions for environmental exposure assessments}, volume={619-620}, ISSN={0048-9697}, url={http://dx.doi.org/10.1016/j.scitotenv.2017.11.093}, DOI={10.1016/j.scitotenv.2017.11.093}, abstractNote={Understanding and simulating the fate and transport of pesticides from a field to adjacent receiving water bodies is critical for estimating long-term environmental exposure concentrations (EECs) in regulatory higher-tier environmental exposure assessments (EEA). The potential of field mitigation practices like vegetative filter strips (VFS) to reduce pesticide pollution is receiving increasing attention. Previous research has proposed a modeling framework that links the US Environmental Protection Agency's (US-EPA) PRZM/EXAMS higher-tier EEA with a process-based VFS model (VFSMOD). This framework was updated to consider degradation and carryover of pesticide residue trapped in the VFS. However, there is disagreement on pesticide degradation assumptions among different regional EEA regulations (i.e. US or European Union), and in particular on how temperature and soil moisture dynamics may affect EECs. This research updated the VFS modeling framework to consider four degradation assumptions and determine if VFS residues and/or EECs differed with each assumption. Two model pesticides (mobile-labile and immobile-persistent) were evaluated for three distinct agroecological scenarios (continental row-crop agriculture, wet maritime agriculture, and dry Mediterranean intensive horticulture) with receiving water bodies and VFS lengths from 0 to 9 m. The degradation assumption was important in long-term assessments to predict VFS pesticide residues (statistically different at p < 0.01). However, due to the relatively small contribution of residues on the total pesticide mass moving through the VFS, degradation assumptions had a negligible impact on EECs. This indicates that, while important differences exist between EU or US EEAs, the choice of pesticide degradation assumption is not a main source of these differences.}, journal={Science of The Total Environment}, publisher={Elsevier BV}, author={Muñoz-Carpena, Rafael and Fox, Garey A. and Ritter, Amy and Perez-Ovilla, Oscar and Rodea-Palomares, Ismael}, year={2018}, month={Apr}, pages={977–987} }
 @article{fox_muñoz-carpena_2018, title={Engineering the design of buffers and vegetative filter strips}, volume={25}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85043326209&partnerID=MN8TOARS}, number={2}, journal={Resource: Engineering and Technology for Sustainable World}, author={Fox, G. and Muñoz-Carpena, R.}, year={2018}, pages={4–5} }
 @article{akay_özer_fox_wilson_2018, title={Fiber Reinforced Sandy Slopes under Groundwater Return Flow}, volume={144}, ISSN={0733-9437 1943-4774}, url={http://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0001300}, DOI={10.1061/(asce)ir.1943-4774.0001300}, abstractNote={AbstractThe instability of earthen embankments caused by subsurface flow draining out of the banks has been a major concern. In an effort to prevent embankment failures, tension resisting synthetic...}, number={5}, journal={Journal of Irrigation and Drainage Engineering}, publisher={American Society of Civil Engineers (ASCE)}, author={Akay, Onur and Özer, A. Tolga and Fox, Garey A. and Wilson, Glenn V.}, year={2018}, month={May}, pages={04018004} }
 @article{guertault_fox_brewer_2018, title={Geomorphic identification of physical habitat features in a large, altered river system}, volume={40}, ISSN={2267-1242}, url={http://dx.doi.org/10.1051/E3SCONF/20184002031}, DOI={10.1051/e3sconf/20184002031}, abstractNote={Altered flow regimes in streams can significantly affect ecosystems and disturb ecological processes, leading to species loss and extinction. Many river management projects use stream classification and habitat assessment approaches to design practical solutions to reverse or mitigate adverse effects of flow regime alteration on stream systems. The objective of this study was to develop a methodology to provide a primary identification of physical habitats in an 80-km long segment of the Canadian River in central Oklahoma. The methodology relied on basic geomorphic variables describing the stream and its floodplain that were derived from aerial imagery and Lidar data using Geographic Information Systems. Geostatistical tests were implemented to delineate habitat units. This approach based on high resolution data and did not require in-site inspection provided a relatively refined habitat delineation, consistent with visual observations. Future efforts will focus on validation via field surveys and coupling with hydro-sedimentary modeling to provide a tool for environmental flow decisions.}, journal={E3S Web of Conferences}, publisher={EDP Sciences}, author={Guertault, Lucie and Fox, Garey and Brewer, Shannon}, editor={Paquier, A. and Rivière, N.Editors}, year={2018}, pages={02031} }
 @article{zhou_fox_miller_mollenhauer_brewer_2018, title={Groundwater flux estimation in streams: A thermal equilibrium approach}, volume={561}, ISSN={0022-1694}, url={http://dx.doi.org/10.1016/J.JHYDROL.2018.04.001}, DOI={10.1016/j.jhydrol.2018.04.001}, abstractNote={Stream and groundwater interactions play an essential role in regulating flow, temperature, and water quality for stream ecosystems. Temperature gradients have been used to quantify vertical water movement in the streambed since the 1960s, but advancements in thermal methods are still possible. Seepage runs are a method commonly used to quantify exchange rates through a series of streamflow measurements but can be labor and time intensive. The objective of this study was to develop and evaluate a thermal equilibrium method as a technique for quantifying groundwater flux using monitored stream water temperature at a single point and readily available hydrological and atmospheric data. Our primary assumption was that stream water temperature at the monitored point was at thermal equilibrium with the combination of all heat transfer processes, including mixing with groundwater. By expanding the monitored stream point into a hypothetical, horizontal one-dimensional thermal modeling domain, we were able to simulate the thermal equilibrium achieved with known atmospheric variables at the point and quantify unknown groundwater flux by calibrating the model to the resulting temperature signature. Stream water temperatures were monitored at single points at nine streams in the Ozark Highland ecoregion and five reaches of the Kiamichi River to estimate groundwater fluxes using the thermal equilibrium method. When validated by comparison with seepage runs performed at the same time and reach, estimates from the two methods agreed with each other with an R2 of 0.94, a root mean squared error (RMSE) of 0.08 (m/d) and a Nash–Sutcliffe efficiency (NSE) of 0.93. In conclusion, the thermal equilibrium method was a suitable technique for quantifying groundwater flux with minimal cost and simple field installation given that suitable atmospheric and hydrological data were readily available.}, journal={Journal of Hydrology}, publisher={Elsevier BV}, author={Zhou, Yan and Fox, Garey A. and Miller, Ron B. and Mollenhauer, Robert and Brewer, Shannon}, year={2018}, month={Jun}, pages={822–832} }
 @article{guertault_fox_2018, title={Impact of Data Availability and Resolution on Long-Term Sedimentation Estimates in a Storage Reservoir}, volume={23}, ISSN={["1943-5584"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85051733278&partnerID=MN8TOARS}, DOI={10.1061/(ASCE)HE.1943-5584.0001699}, abstractNote={AbstractThe sustainability of worldwide reservoirs is threatened by the reduction of their storage capacity caused by continuous sediment accumulation. Many reservoirs are filling in at rates highe...}, number={10}, journal={JOURNAL OF HYDROLOGIC ENGINEERING}, author={Guertault, L. and Fox, G. A.}, year={2018}, month={Oct} }
 @article{orozco-lópez_muñoz-carpena_gao_fox_2018, title={Riparian Vadose Zone Preferential Flow: Review of Concepts, Limitations, and Perspectives}, volume={17}, ISSN={1539-1663}, url={http://dx.doi.org/10.2136/vzj2018.02.0031}, DOI={10.2136/vzj2018.02.0031}, abstractNote={Core Ideas
Riparian ecosystems are hotspots for macropore flow due to their biogeomorphology.
Macropore prevalence can reduce riparian buffer pollution mitigation effectiveness.
Characterization of macropore morphology and connectivity is needed in riparian zones.
An effect of seasonal shallow water table on macropore flow is proposed.
Integration of infiltration–soil moisture–macropore flow model into design tools is needed.
The design and analysis of surface water pollution control practices such as vegetative filter strips and riparian buffers typically focus on surface runoff, with limited attention given to subsurface flow and transport. Field evidence suggests a prevalence of macropore flow (MF) in the riparian vadose zone (RVZ) due to abundant biological activity (e.g., fauna and roots) and steep hydraulic gradients created by the adjacent stream and the presence of a seasonally shallow water table (SWT). Because rapid leaching and subsurface transport of contaminants can be significant with MF, their prevalence in riparian buffers can negate the intended benefits of this widely adopted surface runoff pollution control practice. While theories exist for modeling preferential flow processes, experimental and modeling techniques are still lacking to characterize in situ RVZ macropore network morphologies at the soil profile and landscape scales. Importantly, the presence of a seasonal SWT can increase MF and transport processes neglected in current analyses. Additional research is needed to evaluate holistic modeling frameworks that can represent MF from measurable parameters at the riparian field scale. In this work, we review various MF theories and concepts suitable to RVZ conditions and identify current limitations and knowledge gaps. We emphasize the use of dual‐permeability approaches as a compromise between model complexity and parameter identifiability. We also identify the need for well‐controlled experimental studies using the latest monitoring technology and validation studies at the laboratory and field scales. Only then can decision‐support tools realistically predict the influence of preferential flow processes on the performance of riparian buffers as a surface water quality control practice.}, number={1}, journal={Vadose Zone Journal}, publisher={Wiley}, author={Orozco-López, Enrique and Muñoz-Carpena, Rafael and Gao, Bin and Fox, Garey A.}, year={2018}, pages={180031} }
 @article{castro-bolinaga_fox_2018, title={Streambank Erosion: Advances in Monitoring, Modeling and Management}, volume={10}, ISSN={2073-4441}, url={http://dx.doi.org/10.3390/w10101346}, DOI={10.3390/w10101346}, abstractNote={The special issue “Streambank Erosion: Monitoring, Modeling, and Management” presents recent progress and outlines new research directions through the compilation of 14 research articles that cover topics relevant to the monitoring, modeling, and management of this morphodynamic process. It contributes to our advancement and understanding of how monitoring campaigns can characterize the effect of external drivers, what the capabilities and limitations of numerical models are when predicting the response of the system, and what the effectiveness of different management practices is in order to prevent and mitigate streambank erosion and failure. The present editorial paper summarizes the main outcomes of the special issue, and further expands on some of the remaining challenges within the realm of monitoring, modeling, and managing streambank erosion and failure. First, it highlights the need to better understand the non-linear behavior of erosion rates with increasing applied boundary shear stress when predicting cohesive soil detachment, and accordingly, to adjust the computational procedures that are currently used to obtain erodibility parameters; and second, it emphasizes the need to incorporate process-based modeling of streambank erosion and failure in the design and assessment of stream restoration projects.}, number={10}, journal={Water}, publisher={MDPI AG}, author={Castro-Bolinaga, Celso and Fox, Garey}, year={2018}, month={Sep}, pages={1346} }
 @article{wardinski_guertault_fox_castro-bolinaga_2018, title={Suitability of a Linear Model for Predicting Cohesive Soil Detachment during Jet Erosion Tests}, volume={23}, ISSN={1084-0699 1943-5584}, url={http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0001690}, DOI={10.1061/(asce)he.1943-5584.0001690}, abstractNote={AbstractCohesive soil detachment is a complex process that is typically simulated using simplified mathematical models such as the linear excess shear stress equation or power laws. The assumption ...}, number={9}, journal={Journal of Hydrologic Engineering}, publisher={American Society of Civil Engineers (ASCE)}, author={Wardinski, K. M. and Guertault, L. and Fox, G. A. and Castro-Bolinaga, C. F.}, year={2018}, month={Sep}, pages={06018004} }
 @inproceedings{enlow_fox_. boyer_stoecker_storm_starks_guertault_2017, title={<i>A Modeling Framework for Evaluating Streambank Stabilization Practices for Reach-Scale Sediment Reduction</i>}, url={http://dx.doi.org/10.13031/aim.201700133}, DOI={10.13031/aim.201700133}, abstractNote={<abstract> <b><sc>Abstract.</sc></b> <b>Streambank stabilization techniques are often implemented to reduce sediment loads from unstable streambanks. Process-based models can predict sediment yields with stabilization scenarios prior to implementation. However, a framework does not exist on how to effectively utilize these models to evaluate stabilization measures; instead, many projects rely on empirical approaches that fail to quantify stream-scale impacts. The objective was to develop a framework to evaluate streambank stabilization practices using process-based hydraulic/sediment transport models, public and landowner perception, construction costs, and effectiveness. This framework produces a set of sediment reduction graphs to determine the stabilization length and a second set of graphs to determine the cost. The methodology was applied to Fivemile Creek, located in western Oklahoma. A CONCEPTS simulation was developed for a 10.25-km reach and several stabilization techniques (grade control, riprap toe, and vegetation) were simulated. Vegetation with 2:1 bank slopes was determined to be the most cost-effective stabilization practice. </b>}, booktitle={2017 Spokane, Washington July 16 - July 19, 2017}, publisher={American Society of Agricultural and Biological Engineers}, author={Enlow, Holly K and Fox, Garey A. and . Boyer, Tracy  A. and Stoecker, Art and Storm, Daniel  E. and Starks, Patrick and Guertault, Lucie}, year={2017} }
 @article{miller_fox_2017, title={A tool for drought planning in Oklahoma: Estimating and using drought-influenced flow exceedance curves}, volume={10}, ISSN={2214-5818}, url={http://dx.doi.org/10.1016/J.EJRH.2017.01.001}, DOI={10.1016/j.ejrh.2017.01.001}, abstractNote={The study region is the state of Oklahoma, USA, which has a varied climate. Precipitation increases west to east, and temperature decreases south to north across the state. Accordingly, Oklahoma has been divided into nine Climate Divisions, which reflect those climatic as well as regional differences in agricultural practices. Surface water is the dominant source for public water systems in Oklahoma and these supplies may be impacted by drought or climatic change. Hydrologic modeling is an important component of water resource planning, but may be beyond the budget of smaller communities. To create a freely available tool for initial assessment of drought streamflows, this study uses publicly available long-term precipitation records for climate divisions in Oklahoma to create flow duration curves (FDCs) from the drought-influenced subsets of streamflow records. The FDCs created from those subsets showed increased likelihood of reduced streamflows. The reduced flows were shown to increase water supply risk to run-of-river users. To eliminate the need for users to re-create these analytic steps, study results were compared to published FDCs and reasonable estimates of drought-influenced FDCs were produced by offsetting the expected exceedance by 10%.}, journal={Journal of Hydrology: Regional Studies}, publisher={Elsevier BV}, author={Miller, R.B. and Fox, G.A.}, year={2017}, month={Apr}, pages={35–46} }
 @article{lisenbee_fox_saenz_miller_2017, title={Comparison of Field Jet Erosion Tests and WEPP-Predicted Erodibility Parameters for Varying Land Cover}, volume={60}, ISSN={2151-0032 2151-0040}, url={http://dx.doi.org/10.13031/trans.12012}, DOI={10.13031/trans.12012}, abstractNote={<abstract> <b><sc>Abstract.</sc></b> Hydrologic models are often used to predict erosion and the influence of land cover changes on sediment detachment within a watershed. One such model, the Water Erosion Prediction Project (WEPP), determines the runoff and sediment yield of a given hillslope using input data including slope, climate, soil, and land management. WEPP accepts user inputs or uses empirical equations to determine two major erodibility parameters within the soil input file: critical shear stress (τ<sub>c</sub>) and the erodibility coefficient (k<sub>d</sub>). WEPP also uses adjustment coefficients to account for vegetation and seasonal effects on erodibility. This study evaluated soil erodibility parameters under two distinct land covers: native tallgrass prairie and encroaching eastern redcedar () woodland. The erodibility parameters for each watershed were first estimated using WEPP with rangeland and cropland relationships, using the Rangeland Hydrology and Erosion Model (RHEM), and then determined mechanistically in the field using the Jet Erosion Test (JET). The adjusted k<sub>d</sub> predicted by WEPP for all watersheds was less than the JET-derived k<sub>d</sub> by one to two orders of magnitude. The baseline and adjusted τ<sub>c</sub> from WEPP-cropland were typically within the same order of magnitude as the JET-derived τ<sub>c</sub>. The WEPP erodibility parameters were most directly correlated with the soil texture and were independent of land cover. Alternatively, the JET-derived erodibility parameters were significantly different between the two land covers, with no relationship observed with soil texture. Calibrated WEPP simulations based on the measured runoff response from each watershed did not indicate differences in predicted sediment transport for the various erodibility parameter estimates in the encroached woodland watersheds, but slight differences were observed in the tallgrass prairie watersheds when using the WEPP-estimated rangeland erodibility parameters and the erodibility parameters suggested by RHEM. Note that the differences in predicted sediment yield were functions of the small range in applied shear stress predicted by the model. This study highlighted the use of testing for determining field site erodibility to better incorporate the impacts of land cover on hillslope sediment detachment in hydrologic modeling.}, number={1}, journal={Transactions of the ASABE}, publisher={American Society of Agricultural and Biological Engineers (ASABE)}, author={Lisenbee, W.A. and Fox, Garey and Saenz, A. and Miller, R.B.}, year={2017}, month={Feb}, pages={173–184} }
 @article{kuster_fox_2017, title={Current state of climate education in natural and social sciences in the USA}, volume={141}, ISSN={["1573-1480"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85013434271&partnerID=MN8TOARS}, DOI={10.1007/s10584-017-1918-z}, number={4}, journal={CLIMATIC CHANGE}, author={Kuster, Emma L. and Fox, Garey A.}, year={2017}, month={Apr}, pages={613–626} }
 @article{khanal_fox_2017, title={Detachment characteristics of root-permeated soils from laboratory jet erosion tests}, volume={100}, ISSN={0925-8574}, url={http://dx.doi.org/10.1016/J.ECOLENG.2016.10.081}, DOI={10.1016/j.ecoleng.2016.10.081}, abstractNote={The influence of vegetation on flow and sediment dynamics at various spatial and temporal scales has been well documented. Vegetation may be one of the most effective measures in streambank stabilization. Traditionally, research on the influence of vegetation roots on streambank stabilization has focused on mechanical reinforcement and reduced applied shear stress due to above ground biomass. Few studies have investigated the effect of roots on fluvial detachment of sediment. This study conducted 36 mini-jet erosion tests (mini-JETs) on bare soil samples and 29 mini-JETs on root-permeated soil samples (average root diameters of 0.5 to 1.7 mm) to determine the role of roots in erosion resistance. The research also estimated parameters of the linear excess shear stress model (erodibility coefficient, kd, and critical shear stress, τc) and a nonlinear detachment model called the Wilson Model (b0 and b1) and investigated the correlations between parameters of the two models and root characteristics. Root-permeated soil samples were more erosion resistant at higher shear stress as the τc and b1 parameters were on average higher for the vegetated samples than the bare soil samples. As root diameter increased in the soil samples, erosion rates at high shear stress decreased. The erodibility coefficient parameters (b0 and kd) of both the linear and nonlinear detachment models were negatively and significantly correlated to root diameter through power functions. No significant correlation was detected between critical shear stress or b1 and root parameters which supports conclusions of previous studies. Significant correlations were observed among the parameters of the excess shear stress model and the nonlinear detachment model; especially high correlation was observed between τc and b1 for the vegetated samples. In conclusion, root-permeated soils exhibited lower erosion rates primarily through increasing the required shear stress before detachment.}, journal={Ecological Engineering}, publisher={Elsevier BV}, author={Khanal, Anish and Fox, Garey A.}, year={2017}, month={Mar}, pages={335–343} }
 @article{mcnichol_kassa_fox_miller_guertault_2017, title={Erodibility Parameters Derived from Jet and Flume Erosion Tests on Root-Permeated Soils}, volume={160}, ISSN={["1936-704X"]}, DOI={10.1111/j.1936-704x.2017.03244.x}, abstractNote={Abstract}, number={1}, journal={JOURNAL OF CONTEMPORARY WATER RESEARCH & EDUCATION}, publisher={Wiley-Blackwell}, author={McNichol, Bailey and Kassa, Kayla and Fox, Garey and Miller, Ron and Guertault, Lucie}, year={2017}, month={Apr}, pages={119–131} }
 @article{wilson_nieber_fox_dabney_ursic_rigby_2017, title={Hydrologic connectivity and threshold behavior of hillslopes with fragipans and soil pipe networks}, volume={31}, ISSN={0885-6087}, url={http://dx.doi.org/10.1002/hyp.11212}, DOI={10.1002/hyp.11212}, abstractNote={Abstract}, number={13}, journal={Hydrological Processes}, publisher={Wiley}, author={Wilson, G.V. and Nieber, J.L. and Fox, G.A. and Dabney, S.M. and Ursic, M. and Rigby, J.R.}, year={2017}, month={May}, pages={2477–2496} }
 @article{yimam_ochsner_fox_2017, title={Hydrologic cost-effectiveness ratio favors switchgrass production on marginal croplands over existing grasslands}, volume={12}, ISSN={1932-6203}, url={http://dx.doi.org/10.1371/journal.pone.0181924}, DOI={10.1371/journal.pone.0181924}, abstractNote={Switchgrass (Panicum virgatum L.) has attracted attention as a promising second generation biofuel feedstock. Both existing grasslands and marginal croplands have been suggested as targets for conversion to switchgrass, but the resulting production potentials and hydrologic impacts are not clear. The objectives of this study were to model switchgrass production on existing grasslands (scenario-I) and on marginal croplands that have severe to very severe limitations for crop production (scenario-II) and to evaluate the effects on evapotranspiration (ET) and streamflow. The Soil and Water Assessment Tool (SWAT) was applied to the 1063 km2 Skeleton Creek watershed in north-central Oklahoma, a watershed dominated by grasslands (35%) and winter wheat cropland (47%). The simulated average annual yield (2002–2011) for rainfed Alamo switchgrass for both scenarios was 12 Mg ha-1. Yield varied spatially under scenario-I from 6.1 to 15.3 Mg ha-1, while under scenario-II the range was from 8.2 to 13.8 Mg ha-1. Comparison of average annual ET and streamflow between the baseline simulation (existing land use) and scenario-I showed that scenario-I had 5.6% (37 mm) higher average annual ET and 27.7% lower streamflow, representing a 40.7 million m3 yr-1 streamflow reduction. Compared to the baseline, scenario-II had only 0.5% higher ET and 3.2% lower streamflow, but some monthly impacts were larger. In this watershed, the water yield reduction per ton of biomass production (i.e. hydrologic cost-effectiveness ratio) was more than 5X greater under scenario-I than under scenario-II. These results suggest that, from a hydrologic perspective, it may be preferable to convert marginal cropland to switchgrass production rather than converting existing grasslands.}, number={8}, journal={PLOS ONE}, publisher={Public Library of Science (PLoS)}, author={Yimam, Yohannes Tadesse and Ochsner, Tyson E. and Fox, Garey A.}, editor={Mehdi, BanoEditor}, year={2017}, month={Aug}, pages={e0181924} }
 @article{heeren_fox_penn_halihan_storm_haggard_2017, title={Impact of Macropores and Gravel Outcrops on Phosphorus Leaching at the Plot Scale in Silt Loam Soils}, volume={60}, ISSN={2151-0040}, url={http://dx.doi.org/10.13031/trans.12015}, DOI={10.13031/trans.12015}, abstractNote={Abstract.}, number={3}, journal={Transactions of the ASABE}, publisher={American Society of Agricultural and Biological Engineers (ASABE)}, author={Heeren, Derek M. and Fox, Garey A. and Penn, Chad J. and Halihan, Todd and Storm, Daniel E. and Haggard, Brian E.}, year={2017}, pages={823–835} }
 @article{mittelstet_storm_fox_allen_2017, title={Modeling Streambank Erosion on Composite Streambanks on a Watershed Scale}, volume={60}, ISSN={2151-0040}, url={http://dx.doi.org/10.13031/trans.11666}, DOI={10.13031/trans.11666}, abstractNote={Abstract.}, number={3}, journal={Transactions of the ASABE}, publisher={American Society of Agricultural and Biological Engineers (ASABE)}, author={Mittelstet, Aaron R. and Storm, Daniel E. and Fox, Garey A. and Allen, Peter M.}, year={2017}, pages={753–767} }
 @article{wilson_wells_kuhnle_fox_nieber_2017, title={Sediment detachment and transport processes associated with internal erosion of soil pipes}, volume={43}, ISSN={0197-9337}, url={http://dx.doi.org/10.1002/esp.4147}, DOI={10.1002/esp.4147}, abstractNote={Abstract}, number={1}, journal={Earth Surface Processes and Landforms}, publisher={Wiley}, author={Wilson, Glenn V. and Wells, Robert and Kuhnle, Roger and Fox, Garey and Nieber, John}, year={2017}, month={May}, pages={45–63} }
 @article{mittelstet_storm_fox_2017, title={Testing of the Modified Streambank Erosion and Instream Phosphorus Routines for the SWAT Model}, volume={53}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85006117677&partnerID=MN8TOARS}, DOI={10.1111/1752-1688.12485}, abstractNote={Abstract}, number={1}, journal={Journal of the American Water Resources Association}, author={Mittelstet, A.R. and Storm, D.E. and Fox, G.A.}, year={2017}, pages={101–114} }
 @article{fox_kuster_fox_2017, title={The Importance of Scientific Publishing: Teaching an Undergraduate How to Swim the Entire Length of the Pool}, volume={160}, ISSN={["1936-704X"]}, DOI={10.1111/j.1936-704x.2017.03236.x}, abstractNote={Journal of Contemporary Water Research & Education UCOWR A number of programs are currently available to support undergraduate water research. For example, many academic institutions across the United States offer undergraduate research scholars’ programs. The National Institutes for Water Resources (NIWR) helps the U.S. Geological Survey (USGS) meet the nation’s water needs by “...transferring the latest tools and knowledge to water professionals around the country, training the next generation of water scientists, and tackling emerging water issues in collaboration with USGS scientists.” Numerous projects funded by USGS and NIWR support undergraduate research assistants throughout the states and territories of the United States. The National Science Foundation (NSF) has invested significant resources into their Research Experience for Undergraduates (REU) programs across its directorates, providing key opportunities for undergraduates to participate in summer research experiences during a sixto ten-week period. The United States Department of Agriculture National Institute of Food and Agriculture (USDA NIFA) also funds undergraduate fellowship programs in key challenge areas. Furthermore, the U.S. Environmental Protection Agency (EPA) sponsors a People, Prosperity, and the Planet (P3) Student Design Competition. Many assume that undergraduate research projects are not capable of generating enough high quality information to publish in peerreviewed journals. Often undergraduates are simply acknowledged or less frequently added as lower order co-authors on papers to which they contributed. The students are often not engaged through the complete publication process. Unfortunately, this limits undergraduate students’ opportunities for understanding the entire research paradigm and properly framing their contribution within existing scientific literature, until they get into graduate school. A graduate thesis is often the first major publication for a student. Russell et al. (2007) noted that when undergraduates participate in research they increase their understanding of how to conduct research, their confidence in their research skills, and their awareness of what graduate school might be like. Linn et al. (2015) provided an in-depth review of undergraduate research opportunities, noting that past studies consistently document how students appreciate undergraduate research opportunities. However, they point out that very few studies are able to explicitly measure a student’s understanding of the scientific practice or science concepts. They state that “...less than 10% of the studies validate self-reports with analysis of research products” such as presentations, reports, or publications. Having a goal to publish undergraduate research will more explicitly and thoroughly train an undergraduate to understand the scientific process, better prepare them for graduate studies, and more effectively assess undergraduate research programs. Universities Council on Water Resources Journal of Contemporary Water Research & Education Issue 160, Pages 1-4, April 2017}, number={1}, journal={JOURNAL OF CONTEMPORARY WATER RESEARCH & EDUCATION}, author={Fox, Garey A. and Kuster, Emma L. and Fox, Amanda K.}, year={2017}, month={Apr}, pages={1–4} }
 @article{enlow_fox_guertault_2017, title={Watershed Variability in Streambank Erodibility and Implications for Erosion Prediction}, volume={9}, ISSN={2073-4441}, url={http://dx.doi.org/10.3390/w9080605}, DOI={10.3390/w9080605}, abstractNote={Two fluvial erosion models are commonly used to simulate the erosion rate of cohesive soils: the empirical excess shear stress model and the mechanistic Wilson model. Both models include two soil parameters, the critical shear stress (τc) and the erodibility coefficient (kd) for the excess shear stress model and b0 and b1 for the Wilson model. Jet erosion tests (JETs) allow for in-situ determination of these parameters. JETs were completed at numerous sites along two streams in each the Illinois River and Fort Cobb Reservoir watersheds. The objectives were to use JET results from these streambank tests to investigate variability of erodibility parameters on the watershed scale and investigate longitudinal trends in streambank erodibility. The research also determined the impact of this variability on lateral retreat predicted by a process-based model using both the excess shear stress model and the Wilson model. Parameters derived from JETs were incorporated into a one-dimensional process-based model to simulate bank retreat for one stream in each watershed. Erodibility parameters varied by two to five and one to two orders of magnitude in the Illinois River watershed and Fort Cobb Reservoir watershed, respectively. Less variation was observed in predicted retreat by a process-based model compared to the input erodibility parameters. Uncalibrated erodibility parameters and simplified applied shear stress estimates failed to match observed lateral retreats suggesting the need for model calibration and/or advanced flow modeling.}, number={8}, journal={Water}, publisher={MDPI AG}, author={Enlow, Holly and Fox, Garey and Guertault, Lucie}, year={2017}, month={Aug}, pages={605} }
 @inproceedings{akay_özer_fox_wilson_2016, title={Behavior of Fiber-Reinforced Sandy Slopes under Seepage}, ISBN={9780784479858}, url={http://dx.doi.org/10.1061/9780784479858.041}, DOI={10.1061/9780784479858.041}, abstractNote={Seepage flow is a major contributor to instability of natural hill slopes, river banks and engineered embankments. In order to increase the factor of safety, an emerging technology involves the inclusion of synthetic fibers in the soil. The addition of tension resisting fibers has a favorable effect on strength properties of sandy soils. In this study, laboratory lysimeter experiments were conducted on fiber reinforced slopes with two different values of constant pressure head boundary condition (25 and 50 cm) in the water reservoir. Fiber reinforced sand was compacted in the soil compartment of the lysimeter to obtain a slope with dimensions of 55 cm height, 20 cm width, and 100 cm base length. The gravimetric fiber content (percentage of dry weight of sand) was selected as 1% after reviewing the results of comprehensive triaxial compression tests on fiber reinforced sand specimens with varying fibrillated polypropylene fiber (12 mm long) contents from 0.1 to 1%. This study included slope stability modeling in order to quantify the global factor of safety. The triaxial compression tests indicated the increase in peak deviatoric stress with increase in fiber content. The fiber reinforced sand slope was stable against seepage conditions which would otherwise cause a shallow-seated failure of the non-remediated slope under 25 cm water pressure head. In addition, fiber reinforced sand slope maintained its global stability under 50 cm water pressure head which caused a deep-seated failure of the unreinforced slope. However, sloughing at the toe occurred under 50 and 55 cm water pressure head.}, booktitle={World Environmental and Water Resources Congress 2016}, publisher={American Society of Civil Engineers}, author={Akay, Onur and Özer, A. Tolga and Fox, Garey A. and Wilson, Glenn V.}, year={2016}, month={May}, pages={397–406} }
 @article{khanal_klavon_fox_daly_2016, title={Comparison of Linear and Nonlinear Models for Cohesive Sediment Detachment: Rill Erosion, Hole Erosion Test, and Streambank Erosion Studies}, volume={142}, ISSN={0733-9429 1943-7900}, url={http://dx.doi.org/10.1061/(ASCE)HY.1943-7900.0001147}, DOI={10.1061/(ASCE)HY.1943-7900.0001147}, abstractNote={AbstractCohesive sediment detachment is typically modeled for channels, levees, spillways, earthen dams, and internal erosion by using a linear excess shear stress approach. However, mechanistic nonlinear detachment models, such as the Wilson model, have recently been proposed in the literature. Questions exist as to the appropriateness of nonlinear relationships between applied shear stress and the erosion rate. Therefore, the objective of this research was to test the appropriateness of linear and nonlinear detachment models for cohesive sediment detachment using three data sets: (1) rill erodibility studies across a limited range of applied shear stress (0.9–21.4 Pa), (2) hole erosion tests (HETs) across a wide range of applied shear stress (12.6–62.0 Pa), and (3) streambank erodibility as quantified by jet erosion tests (JETs) for the linear excess shear stress equation and the nonlinear Wilson model across a small range of shear stress (1–4 Pa). The Wilson model was also incorporated into the bank st...}, number={9}, journal={Journal of Hydraulic Engineering}, publisher={American Society of Civil Engineers (ASCE)}, author={Khanal, A. and Klavon, K. R. and Fox, G. A. and Daly, E. R.}, year={2016}, month={Sep}, pages={04016026} }
 @article{daly_fox_fox_2016, title={Correlating Site-Scale Erodibility Parameters from Jet Erosion Tests to Soil Physical Properties}, volume={59}, ISSN={2151-0032 2151-0040}, url={http://dx.doi.org/10.13031/trans.59.11309}, DOI={10.13031/trans.59.11309}, abstractNote={Abstract. One of the most commonly used methods of measuring erodibility parameters, i.e., critical shear stress (τc) and erodibility coefficient (kd), of cohesive soils is the Jet Erosion Test (JET). While numerous factors influence the erodibility parameters, the JET provides an in situ measurement technique. However, in many cases where erodibility parameters are required for simulating channel erosion processes, the erodibility parameters are not characterized in situ but estimated empirically based on soil physical properties with relationships that may not be good predictors for all streambanks. The objectives of this study were to investigate the correlation between the erodibility parameters measured with JETs and soil physical properties at a site-specific scale and across three unique streambanks. A total of 74 JETs were conducted within visually homogeneous streambank layers at three sites in Oklahoma along with measurements of soil physical parameters such as texture, bulk density, moisture content, and water and soil temperatures. At the site scale, τc and kd varied by up to three orders of magnitude. Neither multiple linear regressions nor principal components regressions suggested any consistent strongly correlated variables. Therefore, erodibility parameters measured in this study could not be predicted based solely on soil physical properties. It was concluded that τc and kd must be measured in situ and cannot be estimated from empirical relationships due to the heterogeneous nature of soil and the variability in subaerial processes, even within visually homogeneous streambank layers. More research is needed in order to correlate erodibility parameters to other soil parameters and quantify the role of subaerial processes, such as seepage, soil desiccation, and freeze-thaw cycles, on erodibility in order to incorporate spatial variability of erodibility parameters into stability and channel evolution models.}, number={1}, journal={Transactions of the ASABE}, publisher={American Society of Agricultural and Biological Engineers (ASABE)}, author={Daly, E.R. and Fox, G.A. and Fox, A.K.}, year={2016}, month={Feb}, pages={115–128} }
 @article{criswell_al-madhhachi_fox_miller_2016, title={Deriving Erodibility Parameters of a Mechanistic Detachment Model for Gravels}, volume={59}, ISSN={2151-0032 2151-0040}, url={http://dx.doi.org/10.13031/trans.59.11490}, DOI={10.13031/trans.59.11490}, abstractNote={Abstract. Recent research has proposed the use of a mechanistic detachment model, called the Wilson model, in place of the excess shear stress equation for predicting the detachment of cohesive soils during erosion. However, this mechanistic detachment model was also proposed as being valid for noncohesive soils but with limited evaluation. Such erodibility parameters are often needed in erosion models developed using a single detachment rate approach for both cohesive and noncohesive soils. Therefore, the objectives of this research were to evaluate the applicability of the Wilson model for noncohesive soils and to evaluate a procedure for deriving the erodibility parameters (b 0 and b 1 ) from flume experiments. Gravel samples were extracted from composite streambanks on the Barren Fork Creek in eastern Oklahoma. The samples were sieved into particle size classes, and then at least triplicate flume experiments were performed (gravel sizes of 0.45, 0.60, 1.30, and 1.90 cm). Flow rate, water surface elevation, and scour depth were measured to estimate the energy slope, scour rate, and effective shear stress. The Wilson model was fit to the scour depth data to derive b 0 and b 1 using the generalized reduced gradient method to minimize the error between the predicted and measured scour. Constraints were required within the solver routine to limit potential solutions of b 1 . Similar to cohesive soils, b 0 and b 1 had similar relationships to but different magnitudes than the erodibility coefficient (k d ) and critical shear stress (I„ c ) for these gravels. Equivalent b 1 -I„ c relationships were derived from the flume tests as compared to the theoretical b 1 -I„ c relationship in the Wilson model. The b 0 -b 1 and k d -I„ c relationships followed power law relationships. This research supports the applicability of the nonlinear mechanistic detachment model for noncohesive gravels.}, number={1}, journal={Transactions of the ASABE}, publisher={American Society of Agricultural and Biological Engineers (ASABE)}, author={Criswell, D.T. and Al-Madhhachi, A.T. and Fox, G.A. and Miller, R.B.}, year={2016}, month={Feb}, pages={145–151} }
 @article{purvis_fox_penn_storm_parnell_2016, title={Estimating Streambank Phosphorus Loads at the Watershed Scale with Uncertainty Analysis Approach}, volume={21}, ISSN={1084-0699 1943-5584}, url={http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0001402}, DOI={10.1061/(ASCE)HE.1943-5584.0001402}, abstractNote={AbstractStreambank nutrient loading rates are a growing concern within many watersheds. Only a few studies exist on streambank soil chemistry and phosphorus (P) concentrations, spatial distributions in watersheds, and P loading rates with a consideration of the potential uncertainty associated with the estimates. More so, limited studies compare streambank P loading for streams within similar watersheds and with similar land use and management. The objectives of this research included (1) quantifying the magnitude and spatial distribution of soil pH, electrical conductivity (EC), total P concentration, dissolved P concentration, and the degree of P saturation of streambanks in a watershed; (2) quantifying whether water-soluble phosphorus (WSP) and total phosphorus (TP) loads entering the stream from streambanks are significant based on a combined mass balance and uncertainty analysis approach; and (3) contrasting streambank P concentrations and loadings between two similar streams: Spavinaw Creek (SC) ver...}, number={9}, journal={Journal of Hydrologic Engineering}, publisher={American Society of Civil Engineers (ASCE)}, author={Purvis, R. A. and Fox, G. A. and Penn, C. J. and Storm, D. E. and Parnell, A.}, year={2016}, month={Sep}, pages={04016028} }
 @article{klavon_fox_guertault_langendoen_enlow_miller_khanal_2016, title={Evaluating a process-based model for use in streambank stabilization: insights on the Bank Stability and Toe Erosion Model (BSTEM)}, volume={42}, ISSN={0197-9337}, url={http://dx.doi.org/10.1002/ESP.4073}, DOI={10.1002/esp.4073}, abstractNote={Abstract}, number={1}, journal={Earth Surface Processes and Landforms}, publisher={Wiley}, author={Klavon, Kate and Fox, Garey and Guertault, Lucie and Langendoen, Eddy and Enlow, Holly and Miller, Ron and Khanal, Anish}, year={2016}, month={Dec}, pages={191–213} }
 @article{penn_bowen_mcgrath_nairn_fox_brown_wilson_gill_2016, title={Evaluation of a universal flow-through model for predicting and designing phosphorus removal structures}, volume={151}, ISSN={0045-6535}, url={http://dx.doi.org/10.1016/J.CHEMOSPHERE.2016.02.105}, DOI={10.1016/j.chemosphere.2016.02.105}, abstractNote={Phosphorus (P) removal structures have been shown to decrease dissolved P loss from agricultural and urban areas which may reduce the threat of eutrophication. In order to design or quantify performance of these structures, the relationship between discrete and cumulative removal with cumulative P loading must be determined, either by individual flow-through experiments or model prediction. A model was previously developed for predicting P removal with P sorption materials (PSMs) under flow-through conditions, as a function of inflow P concentration, retention time (RT), and PSM characteristics. The objective of this study was to compare model results to measured P removal data from several PSM under a range of conditions (P concentrations and RT) and scales ranging from laboratory to field. Materials tested included acid mine drainage residuals (AMDRs), treated and non-treated electric arc furnace (EAF) steel slag at different size fractions, and flue gas desulfurization (FGD) gypsum. Equations for P removal curves and cumulative P removed were not significantly different between predicted and actual values for any of the 23 scenarios examined. However, the model did tend to slightly over-predict cumulative P removal for calcium-based PSMs. The ability of the model to predict P removal for various materials, RTs, and P concentrations in both controlled settings and field structures validate its use in design and quantification of these structures. This ability to predict P removal without constant monitoring is vital to widespread adoption of P removal structures, especially for meeting discharge regulations and nutrient trading programs.}, journal={Chemosphere}, publisher={Elsevier BV}, author={Penn, Chad and Bowen, James and McGrath, Joshua and Nairn, Robert and Fox, Garey and Brown, Glenn and Wilson, Stuart and Gill, Clinton}, year={2016}, month={May}, pages={345–355} }
 @article{miller_heeren_fox_halihan_storm_2016, title={Heterogeneity influences on stream water–groundwater interactions in a gravel-dominated floodplain}, volume={61}, ISSN={0262-6667 2150-3435}, url={http://dx.doi.org/10.1080/02626667.2014.992790}, DOI={10.1080/02626667.2014.992790}, abstractNote={ABSTRACT Floodplains are composed of complex depositional patterns of ancient and recent stream sediments, and research is needed to address the manner in which coarse floodplain materials affect stream–groundwater exchange patterns. Efforts to understand the heterogeneity of aquifers have utilized numerous techniques typically focused on point-scale measurements; however, in highly heterogeneous settings, the ability to model heterogeneity is dependent on the data density and spatial distribution. The objective of this research was to investigate the correlation between broad-scale methodologies for detecting heterogeneity and the observed spatial variability in stream/groundwater interactions of gravel-dominated alluvial floodplains. More specifically, this study examined the correlation between electrical resistivity (ER) and alluvial groundwater patterns during a flood event at a site on Barren Fork Creek, in the Ozark ecoregion of Oklahoma, USA, where chert gravels were common both as streambed and as floodplain material. Water table elevations from groundwater monitoring wells for a flood event on 1–5 May 2009 were compared to ER maps at various elevations. Areas with high ER matched areas with lower water table slope at the same elevation. This research demonstrated that ER approaches were capable of indicating heterogeneity in surface water–groundwater interactions, and that these heterogeneities were present even in an aquifer matrix characterized as highly conductive. Portions of gravel-dominated floodplain vadose zones characterized by high hydraulic conductivity features can result in heterogeneous flow patterns when the vadose zone of alluvial floodplains activates during storm events. EDITOR D. Koutsoyiannis; ASSOCIATE EDITOR X. Chen}, number={4}, journal={Hydrological Sciences Journal}, publisher={Informa UK Limited}, author={Miller, R.B. and Heeren, D.M. and Fox, G.A. and Halihan, T. and Storm, D.E.}, year={2016}, month={Feb}, pages={741–750} }
 @article{fox_sheshukov_cruse_kolar_guertault_gesch_dutnell_2016, title={Reservoir Sedimentation and Upstream Sediment Sources: Perspectives and Future Research Needs on Streambank and Gully Erosion}, volume={57}, ISSN={0364-152X 1432-1009}, url={http://dx.doi.org/10.1007/S00267-016-0671-9}, DOI={10.1007/s00267-016-0671-9}, abstractNote={The future reliance on water supply and flood control reservoirs across the globe will continue to expand, especially under a variable climate. As the inventory of new potential dam sites is shrinking, construction of additional reservoirs is less likely compared to simultaneous flow and sediment management in existing reservoirs. One aspect of this sediment management is related to the control of upstream sediment sources. However, key research questions remain regarding upstream sediment loading rates. Highlighted in this article are research needs relative to measuring and predicting sediment transport rates and loading due to streambank and gully erosion within a watershed. For example, additional instream sediment transport and reservoir sedimentation rate measurements are needed across a range of watershed conditions, reservoir sizes, and geographical locations. More research is needed to understand the intricate linkage between upland practices and instream response. A need still exists to clarify the benefit of restoration or stabilization of a small reach within a channel system or maturing gully on total watershed sediment load. We need to better understand the intricate interactions between hydrological and erosion processes to improve prediction, location, and timing of streambank erosion and failure and gully formation. Also, improved process-based measurement and prediction techniques are needed that balance data requirements regarding cohesive soil erodibility and stability as compared to simpler topographic indices for gullies or stream classification systems. Such techniques will allow the research community to address the benefit of various conservation and/or stabilization practices at targeted locations within watersheds.}, number={5}, journal={Environmental Management}, publisher={Springer Science and Business Media LLC}, author={Fox, G. A. and Sheshukov, A. and Cruse, R. and Kolar, R. L. and Guertault, L. and Gesch, K. R. and Dutnell, R. C.}, year={2016}, month={Feb}, pages={945–955} }
 @article{purvis_fox_2016, title={Streambank sediment loading rates at the watershed scale and the benefit of riparian protection}, volume={41}, ISSN={0197-9337}, url={http://dx.doi.org/10.1002/ESP.3901}, DOI={10.1002/esp.3901}, abstractNote={Abstract}, number={10}, journal={Earth Surface Processes and Landforms}, publisher={Wiley}, author={Purvis, Rebecca A. and Fox, Garey A.}, year={2016}, month={Feb}, pages={1327–1336} }
 @article{fox_purvis_penn_2016, title={Streambanks: A net source of sediment and phosphorus to streams and rivers}, volume={181}, ISSN={0301-4797}, url={http://dx.doi.org/10.1016/J.JENVMAN.2016.06.071}, DOI={10.1016/j.jenvman.2016.06.071}, abstractNote={Sediment and phosphorus (P) are two primary pollutants of surface waters. Many studies have investigated loadings from upland sources or even streambed sediment, but in many cases, limited to no data exist to determine sediment and P loading from streambanks on a watershed scale. The objectives of this paper are to review the current knowledge base on streambank erosion and failure mechanisms, streambank P concentrations, and streambanks as P loading sources and then also to identify future research needs on this topic. In many watersheds, long-term loading of soil and associated P to stream systems has created a source of eroded soil and P that may interact with streambank sediment and be deposited in floodplains downstream. In many cases streambanks were formed from previously eroded and deposited alluvial material and so the resulting soils possess unique physical and chemical properties from adjacent upland soils. Streambank sediment and P loading rates depend explicitly on the rate of streambank migration and the concentration of P stored within bank materials. From the survey of literature, previous studies report streambank total P concentrations that consistently exceeded 250 mg kg(-1) soil. Only a few studies also reported water soluble or extractable P concentrations. More research should be devoted to understanding the dynamic processes between different P pools (total P versus bioavailable P), and sorption or desorption processes under varying hydraulic and stream chemistry conditions. Furthermore, the literature reported that streambank erosion and failure and gully erosion were reported to account for 7-92% of the suspended sediment load within a channel and 6-93% of total P. However, significant uncertainty can occur in such estimates due to reach-scale variability in streambank migration rates and future estimates should consider the use of uncertainty analysis approaches. Research is also needed on the transport rates of dissolved and sediment-bound P through the entire stream system of a watershed to identify critical upland and/or near-stream conservation practices. Extensive monitoring of the impact of restoration/rehabilitation efforts on reducing sediment and P loading are limited. From an application standpoint, streambank P contributions to streams should be more explicitly accounted for in developing total maximum daily loads in watersheds.}, journal={Journal of Environmental Management}, publisher={Elsevier BV}, author={Fox, Garey A. and Purvis, Rebecca A. and Penn, Chad J.}, year={2016}, month={Oct}, pages={602–614} }
 @inproceedings{woytowitz_brewer_fox_2016, title={Thermal regimes and fish assemblages in a restored Oklahoma stream}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85009101198&partnerID=MN8TOARS}, DOI={10.13031/aim.20162377956}, abstractNote={<abstract> <b><sc>Abstract.</sc></b> Stream restoration aims to re-establish the structure, function, and diversity of streams that have been altered from their natural state. Effective restoration approaches address both physical and ecological aspects of stream environments. To assess the physical and ecological condition of a restored Oklahoma stream, this study investigated spatial and temporal variation in water temperatures around in-stream structures, along vertical profiles, and in shaded versus nonshaded reaches using automated temperature loggers. Also, fish species richness and diversity (Shannon-Weiner diversity index (H‘)) were quantified at nonshaded and shaded locations by sampling in the morning and afternoon using a seine. All research was conducted within undisturbed and restored reaches of Cow Creek, a third-order stream in Stillwater, OK. Mann-Whitney U tests, Kruskal-Wallis one-way analysis of variance (ANOVA) by ranks tests, and Pearson product-moment correlation coefficient (r) calculations were performed on the fish diversity measures. Results revealed that maximum daily water temperature was generally warmer downstream of in-stream structures and that fish species richness and H‘ were significantly different at different times of day but these differences were not related to riparian shading. This suggests that in-stream structures affect thermal regimes and that water temperature, more so than light, plays an important role in shaping fish distributions. In the future, stream restoration projects would benefit from considering the influence of in-stream structures on water temperature and water temperature on aquatic organisms.}, booktitle={2016 American Society of Agricultural and Biological Engineers Annual International Meeting, ASABE 2016}, author={Woytowitz, E.L. and Brewer, S.K. and Fox, G.A.}, year={2016} }
 @article{khanal_fox_al-madhhachi_2016, title={Variability of Erodibility Parameters from Laboratory Mini Jet Erosion Tests}, volume={21}, ISSN={1084-0699 1943-5584}, url={http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0001404}, DOI={10.1061/(ASCE)HE.1943-5584.0001404}, abstractNote={AbstractApplication of jet erosion tests (JETs) to study in situ erodibility is gaining popularity. New versions of the JET (original JET versus mini-JET) and new data analysis techniques have introduced questions regarding their operation and data collection procedures. One of the major issues regarding JETs is the high degree of variability of the erodibility parameters (i.e., erodibility coefficient, kd, and critical shear stress, τc). This variability has been attributed to heterogeneity in different soil properties under natural field conditions, but limited research has quantified variability under controlled laboratory conditions, especially for the newer mini-JET. This study uniquely conducted 20 mini-JETs under controlled laboratory conditions on each of two soil types of contrasting texture. Mini-JETs were conducted in situ on streambanks of these same soils in previous research. The laboratory mini-JETs predicted similar values of most parameters with much less variability than in the field. Th...}, number={10}, journal={Journal of Hydrologic Engineering}, publisher={American Society of Civil Engineers (ASCE)}, author={Khanal, A. and Fox, G. A. and Al-Madhhachi, A. T.}, year={2016}, month={Oct}, pages={04016030} }
 @article{muñoz-carpena_ritter_fox_perez-ovilla_2015, title={Does mechanistic modeling of filter strip pesticide mass balance and degradation processes affect environmental exposure assessments?}, volume={139}, ISSN={0045-6535}, url={http://dx.doi.org/10.1016/J.CHEMOSPHERE.2015.07.010}, DOI={10.1016/j.chemosphere.2015.07.010}, abstractNote={Vegetative filter strips (VFS) are a widely adopted practice for limiting pesticide transport from adjacent fields to receiving waterbodies. The efficacy of VFS depends on site-specific input factors. To elucidate the complex and non-linear relationships among these factors requires a process-based modeling framework. Previous research proposed linking existing higher-tier environmental exposure models with a well-tested VFS model (VFSMOD). However, the framework assumed pesticide mass stored in the VFS was not available for transport in subsequent storm events. A new pesticide mass balance component was developed to estimate surface pesticide residue trapped in the VFS and its degradation between consecutive runoff events. The influence and necessity of the updated framework on acute and chronic estimated environmental concentrations (EECs) and percent reductions in EECs were investigated across three, 30-year U.S. EPA scenarios: Illinois corn, California tomato, and Oregon wheat. The updated framework with degradation predicted higher EECs than the existing framework without degradation for scenarios with greater sediment transport, longer VFS lengths, and highly sorbing and persistent pesticides. Global sensitivity analysis (GSA) assessed the relative importance of mass balance and degradation processes in the context of other input factors like VFS length (VL), organic-carbon sorption coefficient (Koc), and soil and water half-lives. Considering VFS pesticide residue and degradation was not important if single, large runoff events controlled transport, as is typical for higher percentiles considered in exposure assessments. Degradation processes become more important when considering percent reductions in acute or chronic EECs, especially under scenarios with lower pesticide losses.}, journal={Chemosphere}, publisher={Elsevier BV}, author={Muñoz-Carpena, Rafael and Ritter, Amy and Fox, Garey A. and Perez-Ovilla, Oscar}, year={2015}, month={Nov}, pages={410–421} }
 @inproceedings{purvis_fox_penn_storm_2015, place={St. Joseph, Michigan}, title={Estimating Streambank Phosphorus Loads: How much Phosphorus Do Streambanks Contribute at the Watershed Scale?}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84951279175&partnerID=MN8TOARS}, DOI={10.13031/aim.20152176505}, abstractNote={<abstract> <b>Abstract.</b> Nutrient and sediment loading from streambanks are a growing concern within many watersheds. However, there are few studies on streambank phosphorus (P) concentrations and spatial distributions in watersheds. The objectives of this research included (i) quantifying the magnitude of and spatial distribution of streambank P concentrations along a stream system in a watershed with historical poultry litter application, (ii) quantifying the amount of water soluble phosphorus (WSP) and total phosphorus (TP) entering the stream from streambanks, and (iii) comparing streambank P concentrations and loading between two unique streams in the same ecoregion. Soil samples were taken along Spavinaw Creek in eastern Oklahoma and were processed to measure pH, electrical conductivity (EC), WSP, and TP. The pH and EC increased with distance from the confluence at Lake Eucha. There was no clear longitudinal trend in WSP and TP. Using estimated sediment loading (727 x 10<sup>6</sup> kg) from aerial images, it was estimated from 2003-2013 there was 2.4 x 10<sup>2</sup> kg WSP and 1.5 x 10<sup>5</sup> kg TP loaded into Spavinaw Creek from streambanks in Oklahoma. LOADEST, a nutrient load estimator created by the United States Geological Services (USGS), was used to estimate in-stream phosphorus loads. In-stream estimates were an order of magnitude larger for WSP and comparable for TP. A previous study performed a similar analysis along Barren Fork Creek (BFC) in the Illinois River watershed. Both Spavinaw Creek and BFC flow through the Ozarks ecoregion and have cherty topsoil with an underlying gravel layer. Comparison of P loading between the two systems showed that WSP in BFC was an order of magnitude higher while TP was on the same order of magnitude. Streambank P loading rates are dependent on the stream system; therefore each stream needs to be individually studied in order to gain a better understanding of the specific loadings from streambanks.}, number={152176505}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2015}, publisher={American Society of Agricultural and Biological Engineers}, author={Purvis, R.A. and Fox, G.A. and Penn, C.J. and Storm, D.E.}, year={2015}, pages={544–561} }
 @inproceedings{taghvaeian_fox_boman_warren_2015, title={Evaluating the impact of drought on surface and groundwater dependent irrigated agriculture in western Oklahoma}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84969752937&partnerID=MN8TOARS}, booktitle={Joint ASABE/IA Irrigation Symposium 2015: Emerging Technologies for Sustainable Irrigation}, author={Taghvaeian, S. and Fox, G. and Boman, R. and Warren, J.}, year={2015}, pages={379–385} }
 @article{heeren_fox_storm_2015, title={Heterogeneity of Infiltration Rates in Alluvial Floodplains as Measured with a Berm Infiltration Technique}, volume={58}, ISSN={2151-0032 2151-0040}, url={http://dx.doi.org/10.13031/trans.58.11056}, DOI={10.13031/trans.58.11056}, abstractNote={Hydrologic heterogeneities (e.g., macropores and gravel outcrops) in floodplains are hypothesized to play an integral role in impacting flow and leaching between the soil surface and shallow alluvial aquifers, which are intricately connected to streams. Infiltration is often assumed to be uniform, but this neglects the spatial variability common in aniso- tropic, heterogeneous alluvial floodplain soils. The objective of this research was to quantify infiltration and hydraulic conductivity across a range of scales (point to 100 m 2 ) using a berm infiltration technique. Plot-scale leaching experi- ments were performed across a range of soil types at each of three floodplain sites in northeastern Oklahoma and north- western Arkansas. Plots maintained a constant head of 2 to 9 cm for up to 52 h. Effective saturated hydraulic conductivity (Keff), based on plot-scale infiltration rates and a one-dimensional Darcy flow equation, ranged between 0.6 and 68 cm h -1 and varied considerably even within a single floodplain. The Keff was also calculated at the point scale using particle size distributions and Retention Curve (RETC). Point-scale estimates were significantly lower than plot-scale Keff and also failed to capture the variability of Keff. The estimated permeability of the limiting layer reported in soil surveys was con- sistent with point-scale estimates of Keff but was lower than plot-scale Keff at most sites. Tension infiltrometers showed that macropores accounted for approximately 84% to 99% of the total saturated hydraulic conductivity. The plot scale (1 to 100 m 2 ) generally appears to be within the representative elementary volume (REV), but drift in Keff occurs beyond the REV due to changing geomorphic formations. Plot-scale infiltration tests are recommended over point-scale estimates, although only small plots (1 m × 1 m) are necessary.}, number={3}, journal={Transactions of the ASABE}, publisher={American Society of Agricultural and Biological Engineers (ASABE)}, author={Heeren, D.M. and Fox, G.A. and Storm, D.E.}, year={2015}, month={Jun}, pages={733–745} }
 @inproceedings{khanal_klavon_fox_daly_2015, title={Justifying the use of a nonlinear detachment model for cohesive soil erosion}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84951845224&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2015}, author={Khanal, A. and Klavon, K. and Fox, G.A. and Daly, E.R.}, year={2015}, pages={1700–1710} }
 @article{fox_weckler_thomas_2015, title={Linking first-year and senior engineering design teams: Engaging early academic career students in engineering design}, volume={4}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84928342080&partnerID=MN8TOARS}, number={3}, journal={Advances in Engineering Education}, author={Fox, G.A. and Weckler, P. and Thomas, D.}, year={2015} }
 @article{daly_miller_fox_2015, title={Modeling streambank erosion and failure along protected and unprotected composite streambanks}, volume={81}, ISSN={0309-1708}, url={http://dx.doi.org/10.1016/J.ADVWATRES.2015.01.004}, DOI={10.1016/j.advwatres.2015.01.004}, abstractNote={Streambank retreat can be a significant contributor to total sediment and nutrient loading to streams. Process-based bank stability models, such as the Bank Stability and Toe Erosion Model (BSTEM), have been used to determine critical factors affecting streambank erosion and failure such as riparian vegetation and to estimate retreat rates over time. BSTEM has been successfully applied on a number of cohesive streambanks, but less so on composite banks consisting of both cohesive and noncohesive soils in highly sinuous streams. Composite streambanks can exhibit rapid and episodic bank retreat. The objectives of this research were twofold: (i) develop and apply simplified procedures for estimating root cohesion based on above- and below-ground biomass estimates and (ii) systematically apply BSTEM to a series of 10 composite streambanks distributed along the Barren Fork Creek in eastern Oklahoma to assess model sensitivity to root cohesion and model performance in predicting retreat. This research aimed to document the influence of riparian conservation practices on bank retreat rates and evaluated simplistic methods for incorporating such practices into such process-based models. Sites modeled included historically unprotected sites with no riparian vegetation and historically protected sites with riparian vegetation present during all or part of the 2003 to 2010 study period. The lateral retreat ranged from 4.1 to 74.8 m across the 10 sites and was largest at the historically unprotected sites in which retreat averaged 49.2 m. Protected sites had less bank retreat but with more variability in retreat rates per year. With calibration focused on the erodibility parameters, the model was able to match both the observed total amount of retreat as well as the timing of retreat at both the protected and unprotected sites as derived from aerial imagery. During calibration BSTEM was not sensitive to the specific value of the soil cohesion or the additional soil cohesion added due to roots for the cohesive topsoil layer, suggesting that the proposed simplified techniques could be used to estimate root cohesion values. The BSTEM modeling also provided an advantageous assessment tool for evaluating retreat rates compared to in situ bank retreat measurements due to the magnitude and episodic nature of streambank erosion and failures. Process-based models, such as BSTEM, may be necessary to incrementally model bank retreat in order to quantify actual streambank retreat rates and understand mechanisms of failure for the design of stabilization projects.}, journal={Advances in Water Resources}, publisher={Elsevier BV}, author={Daly, Erin R. and Miller, Ronald B. and Fox, Garey A.}, year={2015}, month={Jul}, pages={114–127} }
 @inproceedings{khanal_klavon_fox_daly_2015, title={Nonlinear Detachment Model for Soil Erodibility: Application and Incorporation into a Streambank Erosion and Stability Model}, ISBN={9780784479162}, url={http://dx.doi.org/10.1061/9780784479162.173}, DOI={10.1061/9780784479162.173}, abstractNote={Cohesive sediment transport is typically modeled for channels, levees, spillways, earth dams, and internal erosion using a linear excess shear stress approach. However, mechanistic nonlinear detachment models, such as the Wilson Model, have recently been proposed in the literature. The objective of this research was to determine the suitability of linear and nonlinear detachment models for cohesive sediment transport using three applicable data sets: (1) a rill erodibility study across a limited range of shear stress (0 to 10 Pa), (2) a hole erosion test across an extended range of shear stress (10 to 60 Pa), and (3) streambank erodibility as quantified by jet erosion tests for the linear excess shear stress equation and the nonlinear Wilson Model across a small range of shear stress (2.5 to 7.5 Pa). The Wilson Model was incorporated into the Bank Stability and Toe Erosion Model (BSTEM) as an option for simulating fluvial erosion and used to simulate bank retreat in the streambank erodibility study. Using these three case studies, it was determined that the nonlinear, mechanistic detachment model was more applicable across a wider range in applied shear stress. The use of the nonlinear detachment model also alleviates questions about the most appropriate solution technique for jet erosion tests in deriving erodibility parameters. In situ tests may confine the collection of erosion rate data in terms of the applied shear stress, and therefore, users of these techniques should be aware of the nonlinear behavior of cohesive sediment detachment especially at higher shear stress.}, booktitle={World Environmental and Water Resources Congress 2015}, publisher={American Society of Civil Engineers}, author={Khanal, A. and Klavon, K. and Fox, G. A. and Daly, E. R.}, year={2015}, month={May}, pages={1769–1780} }
 @inproceedings{wanger_fox_wilson_2015, title={Pipeflow experiments to quantify pore-water pressure buildup due to pipe clogging}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84951293420&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2015}, author={Wanger, M.M. and Fox, G.A. and Wilson, G.V.}, year={2015}, pages={204–217} }
 @inproceedings{lisenbee_fox_zou_storm_penn_stebler_mittelstet_2015, title={Predicted influence of eastern redcedar removal on water quantity and quality using the Water Erosion Prediction Project (WEPP)}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84951266363&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2015}, author={Lisenbee, W. and Fox, G. and Zou, C. and Storm, D. and Penn, C. and Stebler, E. and Mittelstet, A.}, year={2015}, pages={534–543} }
 @article{daly_fox_enlow_storm_hunt_2015, title={Site-scale variability of streambank fluvial erodibility parameters as measured with a jet erosion test}, volume={29}, ISSN={0885-6087}, url={http://dx.doi.org/10.1002/HYP.10547}, DOI={10.1002/hyp.10547}, abstractNote={Abstract}, number={26}, journal={Hydrological Processes}, publisher={Wiley}, author={Daly, E. R. and Fox, G. A. and Enlow, H. K. and Storm, D. E. and Hunt, S. L.}, year={2015}, month={Jul}, pages={5451–5464} }
 @article{zhou_wilson_fox_rigby_dabney_2015, title={Soil pipe flow tracer experiments: 2. Application of a streamflow transient storage zone model}, volume={30}, ISSN={0885-6087}, url={http://dx.doi.org/10.1002/HYP.10712}, DOI={10.1002/hyp.10712}, abstractNote={Abstract}, number={8}, journal={Hydrological Processes}, publisher={Wiley}, author={Zhou, Yan and Wilson, G. V. and Fox, G.A. and Rigby, J.R. and Dabney, S.M.}, year={2015}, month={Nov}, pages={1280–1291} }
 @inproceedings{daly_fox_enlow_2015, title={Variability of Fluvial Erodibility Parameters on a Site Scale}, ISBN={9780784479162}, url={http://dx.doi.org/10.1061/9780784479162.182}, DOI={10.1061/9780784479162.182}, abstractNote={The jet erosion test (JET) is one of the most commonly used in situ methods of measuring erodibility parameters (critical shear stress, τc, and erodibility coefficient, kd) of cohesive soils. Several factors can influence the erodibility of cohesive soils, but the influence of these factors is not captured by conducting a few JETs at one discrete point in time and at one location on a streambank. Current practice largely ignores the parameter, spatial, and temporal relationships in erodibility. Furthermore, in many cases the erodibility parameters are not characterized in situ, but estimated empirically with relationships that may not be good predictors for all streambanks. Building upon previous studies, the objectives were to address variability in JET-derived erodibility parameters at a site scale and across a range of soil erodibility with respect to soil parameter correlations, temporal variability, spatial variability, and testing variability. Also, this research estimated the number of JETs required to accurately characterize erodibility. A total of 74 JETs were conducted within visually homogeneous streambank layers at three sites in Oklahoma along with measurements of soil physical parameters such as texture, bulk density, and moisture content. At the site-scale τc and kd varied by up to three orders of magnitude. While there were correlations between the erodibility parameters and measured soil parameters, there were no reliable relationships with strong predictive capabilities at any of the sites for any of the soil parameters. Also, there were no significant multiple linear regressions to predict τc and kd based on more than one soil parameter. Conducting three to five JETs per soil layer on a streambank typically provided an order of magnitude estimate of the erodibility parameters. Because the parameters were log-normally distributed, using empirical equations to predict erosion properties based on soil characteristics will likely contain high uncertainty and thus should be used with caution. This research exemplifies the need to conduct in situ measurements using the JET.}, booktitle={World Environmental and Water Resources Congress 2015}, publisher={American Society of Civil Engineers}, author={Daly, E. R. and Fox, G. A. and Enlow, H. K.}, year={2015}, month={May}, pages={1859–1871} }
 @article{daly_fox_al-madhhachi_storm_2015, title={Variability of fluvial erodibility parameters for streambanks on a watershed scale}, volume={231}, ISSN={0169-555X}, url={http://dx.doi.org/10.1016/J.GEOMORPH.2014.12.016}, DOI={10.1016/j.geomorph.2014.12.016}, abstractNote={Typically the erosion rate of cohesive soils is modeled using the excess shear stress equation, which includes two soil parameters: the erodibility coefficient (kd) and the critical shear stress (τc). Alternatively, a mechanistic detachment rate model, the Wilson model, was recently developed to predict the erosion rate of cohesive soils, also based on two soil parameters: b0 and b1. The Wilson model is proposed as advantageous in terms of being a more mechanistic, fundamentally based erosion equation. The objective of this research was to derive the excess shear stress model parameters (kd and τc) from field jet erosion tests (JETs) on numerous streambanks across the Illinois River watershed in Oklahoma to investigate (i) erodibility parameter variability or uniformity at a river basin scale, (ii) correlations between the derived parameters and soil texture, (iii) influence of solution technique on the estimated erodibility parameters, and (iv) the applicability of predictive relationships between kd and τc. The second objective was to demonstrate the applicability of the mechanistic Wilson model using field JET data and to investigate correlations between the excess shear stress model parameters, kd and τc, and the Wilson model parameters, b0 and b1. Erodibility parameters for streambanks of varying soil texture were measured using a miniature version of the JET device (mini JET). Data from the JETs were used to derive the erodibility parameters using a Blaisdell and scour depth approach. Soil samples were acquired at locations of the JETs to quantify particle size distribution, average particle size (d50) and bulk density. No significant relationships existed between kd or τc and bulk density, d50, percent clay, silt, or sand, or percent clay-silt. Existing empirical relationships should be used with caution considering the variability between the results observed in this research and previous relationships proposed in the literature. Strong correlations were observed between b0 and kd (R2 = 0.62 to 0.89) and between b1 and τc (R2 = 0.31 to 0.96). Therefore, the Wilson model parameters closely resemble the empirical excess shear stress parameters.}, journal={Geomorphology}, publisher={Elsevier BV}, author={Daly, Erin R. and Fox, Garey A. and Al-Madhhachi, Abdul-Sahib T. and Storm, Daniel E.}, year={2015}, month={Feb}, pages={281–291} }
 @article{özer_akay_fox_bartlett_arellano_2014, title={A new method for remediation of sandy slopes susceptible to seepage flow using EPS-block geofoam}, volume={42}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84896818124&partnerID=MN8TOARS}, DOI={10.1016/j.geotexmem.2014.01.003}, abstractNote={Using expanded polystyrene (EPS) geofoam (geofoam block) in slope remediation projects has drawn interest from the civil engineering sector for its ease of application and budget saving features. According to design precedence, all slope remediation applications that use geofoam blocks should incorporate permanent drainage systems to prevent instability of the lightweight geofoam blocks due to hydrostatic and seepage pressures. In this study, a new method for slope remediation using geofoam blocks was tested through physical laboratory experiments. For this purpose, a total of 24 lysimeter (dimensions of 60 cm height, 20 cm width, and 200 cm length) experiments (including duplicates) were conducted in which seepage through a geofoam block slope system were generated with three different constant water levels in the water reservoir of the lysimeter. Geofoam blocks (dimensions of 2.5 cm height, 5 cm width, and 15 cm length) were assembled to form embankment type configuration at the toe section of the sandy slopes. This study also included coupled numerical model simulations that were comprised of variably saturated flow modeling and slope stability modeling which could be implemented successfully for the global static failure analysis of the geofoam block slope system comprised of two mediums with different geotechnical characteristics. In addition to global static stability failure analysis, which involved conventional limit equilibrium analysis for the geofoam block slope system, hydrostatic sliding mechanism was investigated which provided insight into using an overburden concept to increase the resistance against horizontal driving forces. Experimental and numerical modeling results showed that the geofoam block slope system was stable even though the phreatic surface was above the bottom of the geofoam block assemblage. For this reason, the embankment type configuration tested in this study can be considered a viable remediation technique where seepage induced deep-seated global stability and hydrostatic sliding failures are a concern.}, number={2}, journal={Geotextiles and Geomembranes}, author={Özer, A.T. and Akay, O. and Fox, G.A. and Bartlett, S.F. and Arellano, D.}, year={2014}, pages={166–180} }
 @article{penn_heeren_fox_kumar_2014, title={Application of Isothermal Calorimetry to Phosphorus Sorption onto Soils in a Flow-through System}, volume={78}, ISSN={0361-5995}, url={http://dx.doi.org/10.2136/sssaj2013.06.0239}, DOI={10.2136/sssaj2013.06.0239}, abstractNote={Soil Sci. Soc. Am. J. 78:147–156 doi:10.2136/sssaj2013.06.0239 Received 21 June 2013 *Corresponding author: (Chad.penn@okstate.edu). © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. Application of Isothermal Calorimetry to Phosphorus Sorption onto Soils in a Flow-Through System Soil Chemistry}, number={1}, journal={Soil Science Society of America Journal}, publisher={Wiley}, author={Penn, Chad and Heeren, Derek and Fox, Garey and Kumar, Ajay}, year={2014}, month={Jan}, pages={147–156} }
 @inproceedings{zhou_wilson_fox_rigby_dabney_2014, title={Application of a transient storage zone model to soil pipeflow tracer injection experiments}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84911940204&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2014, ASABE 2014}, author={Zhou, Y. and Wilson, G.V. and Fox, G.A. and Rigby, J.R. and Dabney, S.M.}, year={2014}, pages={423–434} }
 @article{akay_özer_fox_2014, title={Assessment of EPS block geofoam with internal drainage for sandy slopes subjected to seepage flow}, volume={21}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84937540677&partnerID=MN8TOARS}, DOI={10.1680/gein.14.00024}, abstractNote={ ABSTRACT: Lightweight expanded polystyrene (EPS) block geofoam (geofoam block) is commonly used as a replacement of the heavy in situ soil during slope remediation in order to reduce driving forces. The design procedure requires the use of permanent drainage systems to alleviate hydrostatic pressures in geofoam block slope systems. In this study, small-scale laboratory lysimeter experiments investigated the behavior of a stabilized sandy slope with a geofoam block slope system experiencing seepage. An internal drainage system was incorporated by grooving dual drainage channels (weep holes) on the top and bottom side of the geofoam blocks. A lysimeter with dimensions of 60 cm height, 20 cm width, and 200 cm length was constructed in the laboratory. Slopes were constructed by compacting sand. The geofoam blocks (2.5 cm height, 5 cm width, and 15 cm length) were placed on the sandy slope face with an angle of 45° in ‘one row' and ‘two rows' configurations. The experiments were conducted under constant water pressure heads (25-, 38-, and 50-cm pressure head boundary conditions) in the water reservoir located at the opposite end of the lysimeter from the geofoam blocks. In general, the lightweight geofoam blocks could not resist earth and hydrostatic pressures under seepage. The back-slope was not self-stable under seepage conditions, and deep-seated global stability failures were observed, except for the remediated slope at the 25- and 38-cm pressure head boundary conditions. The internal drainage system was ineffective at dissipating piezometric pressures at the higher seepage gradients investigated at this lysimeter scale. Numerical slope stability modeling confirmed these observations, predicting a factor of safety below the critical value for global stability in cases where failure was observed. More elaborate geofoam block configurations and/or drainage systems should be used to increase resistance against global stability failure caused by higher seepage gradients. }, number={6}, journal={Geosynthetics International}, author={Akay, O. and Özer, A.T. and Fox, G.A.}, year={2014}, pages={364–376} }
 @inproceedings{daly_miller_fox_2014, title={Bank stability and toe erosion (BSTEM) modeling of bank retreat and riparian tree root protection in composite streambanks}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84911915179&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2014, ASABE 2014}, author={Daly, E.R. and Miller, R.B. and Fox, G.A.}, year={2014}, pages={1232–1249} }
 @article{heeren_fox_storm_2014, title={Berm Method for Quantification of Infiltration at the Plot Scale in High Conductivity Soils}, volume={19}, ISSN={1084-0699 1943-5584}, url={http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000802}, DOI={10.1061/(ASCE)HE.1943-5584.0000802}, abstractNote={AbstractMeasuring infiltration at the plot scale is difficult, especially for high hydraulic conductivity soils. At the plot scale, the infiltration rate is usually calculated by comparing surface runoff to rainfall. Direct measurement of infiltration beyond the point scale is typically limited to locations where land forming (e.g., infiltration pond) has been performed or fields with basin irrigation systems. The standard method for field measurement of point-scale infiltration is the double ring infiltrometer, which is limited in size (typically 30 cm diameter). In this research, a new method is proposed that uses a temporary berm constructed of a water-filled 15-cm diameter vinyl hose with the edges sealed to the soil using bentonite. The berm is capable of confining infiltration plot areas of various sizes (e.g., 1×1 and 3×3  m areas in this research). Water tanks with 0.8 and 4.9  m3 capacity were used to supply water to the plots by gravity flow. A constant head could be maintained within the plot u...}, number={2}, journal={Journal of Hydrologic Engineering}, publisher={American Society of Civil Engineers (ASCE)}, author={Heeren, Derek M. and Fox, Garey A. and Storm, Daniel E.}, year={2014}, month={Feb}, pages={457–461} }
 @article{miller_fox_penn_wilson_parnell_purvis_criswell_2014, title={Estimating sediment and phosphorus loads from streambanks with and without riparian protection}, volume={189}, ISSN={0167-8809}, url={http://dx.doi.org/10.1016/j.agee.2014.03.016}, DOI={10.1016/j.agee.2014.03.016}, abstractNote={In some watersheds, the majority of the total sediment load to streams and rivers is from streambanks, but insufficient data exist on actual loading from this source and the potential protective effect of riparian protection in many watersheds. Using aerial imagery, video reconnaissance for unstable banks, and streambank phosphorus (P) sampling, this research studied streambanks throughout the Barren Fork Creek (BFC) watershed within Oklahoma to address four major objectives: (i) quantify the amount of streambank erosion and failure throughout the watershed, (ii) quantify the magnitude and the intra-site and inter-site spatial variability in streambank soil chemistry, water soluble phosphorus (WSP), and total phosphorus (TP), (iii) quantify the load of WSP and TP from streambanks in the watershed, and (iv) estimate the benefit of riparian management practices. Ten streambank study sites were selected on BFC, including seven sites with existing or historic riparian forest (historically protected, HP), and three with no riparian forest (historically unprotected, HUP). Median and mean streambank migration rates were 9.5 and 17.5 m for the HP sites compared to 37.6 and 49.2 m for the three HUP sites over the seven year period. Total WSP from streambanks on BFC from unprotected and failing banks was approximately 1.2 × 103 kg yr−1, which represented approximately 10% of the dissolved P load estimated from USGS gauges on BFC. The estimated TP load was approximately 9.0 × 104 kg TP yr−1, which exceeded the TP load estimated from gauge data, although TP is largely sediment-bound and thus subject to sediment transport dynamics such as floodplain deposition. Streambanks represented a considerable source of P, and riparian forest sites showed significantly lower rates of retreat. The methodology of using detailed P characterization, lateral retreat rates from aerial photography, and video reconnaissance to characterize bank stability was an effective approach for assessing the WSP and TP load contribution from streambanks.}, journal={Agriculture, Ecosystems & Environment}, publisher={Elsevier BV}, author={Miller, Ronald B. and Fox, Garey A. and Penn, Chad J. and Wilson, Stuart and Parnell, Abigail and Purvis, Rebecca A. and Criswell, Kelsey}, year={2014}, month={May}, pages={70–81} }
 @inproceedings{fox_munoz-carpena_purvis_2014, title={Experimental testing of a new algorithm for analysis of vegetative filter strips with shallow water table effects}, volume={7}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84911472062&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2014, ASABE 2014}, author={Fox, G.A. and Munoz-Carpena, R. and Purvis, R.A.}, year={2014}, pages={4934–4945} }
 @inproceedings{freiberger_heeren_fox_penn_eisenhauer_2014, title={Finite element modeling of long-term phosphorus leaching through macropores in the Ozark ecoregion}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84911473860&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2014, ASABE 2014}, author={Freiberger, R.P. and Heeren, D.M. and Fox, G.A. and Penn, C.J. and Eisenhauer, D.E.}, year={2014}, pages={1862–1881} }
 @article{fox_felice_midgley_wilson_al-madhhachi_2014, title={Laboratory soil piping and internal erosion experiments: Evaluation of a soil piping model for low-compacted soils}, volume={39}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84903981934&partnerID=MN8TOARS}, DOI={10.1002/esp.3508}, abstractNote={ABSTRACT}, number={9}, journal={Earth Surface Processes and Landforms}, author={Fox, G.A. and Felice, R.G. and Midgley, T.L. and Wilson, G.V. and Al-Madhhachi, A.-S.T.}, year={2014}, pages={1137–1145} }
 @inproceedings{fox_weckler_thomas_2014, title={Linking freshmen and senior engineering design teams: Engaging early academic career students in engineering design}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84911864784&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2014, ASABE 2014}, author={Fox, G.A. and Weckler, P.R. and Thomas, D.L.}, year={2014}, pages={435–442} }
 @article{al-madhhachi_fox_hanson_tyagi_bulut_2014, title={Mechanistic Detachment Rate Model to Predict Soil Erodibility Due to Fluvial and Seepage Forces}, volume={140}, ISSN={0733-9429 1943-7900}, url={http://dx.doi.org/10.1061/(ASCE)HY.1943-7900.0000836}, DOI={10.1061/(ASCE)HY.1943-7900.0000836}, abstractNote={AbstractThe erosion rate of cohesive soils is typically computed using an excess shear stress model based on the applied fluvial shear stress. However, no mechanistic approaches are available for incorporating additional forces, such as groundwater seepage into the excess shear stress model parameters. Seepage forces are known to be significant contributors to streambank erosion and failure. The objective of this research was to incorporate seepage forces into a mechanistic fundamental detachment rate model to improve the predictions of the erosion rate of cohesive soils. The new detachment model, which is referred to as the modified Wilson model, was based on two modified dimensional soil parameters (b0 and b1) that included seepage forces due to localized groundwater flow. The proposed model provided a general framework for studying the impact of soil properties, fluid characteristics, and seepage forces on cohesive soil erodibility. Equations were presented for deriving the material parameters from bot...}, number={5}, journal={Journal of Hydraulic Engineering}, publisher={American Society of Civil Engineers (ASCE)}, author={Al-Madhhachi, A. T. and Fox, G. A. and Hanson, G. J. and Tyagi, A. K. and Bulut, R.}, year={2014}, month={May}, pages={04014010} }
 @article{al-madhhachi_fox_hanson_2014, title={Quantifying the erodibility of streambanks and hillslopes due to surface and subsurface forces}, volume={57}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84988589120&partnerID=MN8TOARS}, DOI={10.13031/trans.57.10416}, abstractNote={Abstract. The erosion rate of cohesive soils due to fluvial forces is usually computed using an excess shear stress model. However, no mechanistic approaches are available for incorporating additional forces, such as seepage, into the excess shear stress model parameters. Recent research incorporated subsurface (seepage) forces into a mechanistic detachment rate model for streambeds. The new detachment model, the Modified Wilson model, was based on two modified dimensional parameters (b 0 and b 1 ) that included seepage forces. The objective of this study was to modify the parameters (b 0 and b 1 ) to quantify the influence of seepage on erodibility of cohesive streambanks and to compare the results to those obtained from tests on horizontal beds. A new miniature version of a submerged jet erosion test device (“mini” JET) and a seepage column were utilized to derive the parameters of the Modified Wilson model for a silty sand soil and a clayey sand soil across a range of uniform seepage gradients. The experimental setup was intended to mimic a streambed and a streambank when the “mini” JET and seepage column were placed in vertical and horizontal orientations, respectively. The soils were packed in a standard mold at a uniform bulk density (1.5 to 1.6 Mg m -3 ) near the optimum water content. Seepage forces influenced the observed erosion with a non-uniform influence on b 0 and b 1 as functions of the hydraulic gradient and density. Expected theoretical differences between Wilson model parameters for streambanks and streambeds were not consistently observed for these erodible soils, most likely due to variability in streambed and streambank samples in terms of soil preparation, packing, and seepage gradient establishment. The influence of seepage forces can be predicted by the Modified Wilson model parameters in both vertical and horizontal experimental setups using JETs on soils without seepage. Additional research is needed on the behavior of several mechanistic soil parameters under the influence of seepage.}, number={1}, journal={Transactions of the ASABE}, author={Al-Madhhachi, A.T. and Fox, G.A. and Hanson, G.J.}, year={2014}, pages={1057–1069} }
 @article{miller_heeren_fox_halihan_storm_mittelstet_2014, title={The hydraulic conductivity structure of gravel-dominated vadose zones within alluvial floodplains}, volume={513}, ISSN={0022-1694}, url={http://dx.doi.org/10.1016/j.jhydrol.2014.03.046}, DOI={10.1016/j.jhydrol.2014.03.046}, abstractNote={The floodplains of many gravel-bed streams have a general stratigraphy that consists of a layer of topsoil covering gravel-dominated subsoil. Previous research has demonstrated that this stratigraphy can facilitate preferential groundwater flow through focused linear features, such as paleochannels, or gravelly regions within the vadose zone. These areas within the floodplain vadose zone may provide a route for interactions between the floodplain surface and alluvial groundwater, effectively extending the hyporheic zone across the floodplain during high stream stage. The objective of this research was to assess the structure and scale of texture heterogeneity within the vadose zone within the gravel subsoils of alluvial floodplains using resistivity data combined with hydraulic testing and sediment sampling of the vadose zone. Point-scale and broad-scale methodologies in combination can help us understand spatial heterogeneity in hydraulic conductivity without the need for a large number of invasive hydraulic tests. The evaluated sites in the Ozark region of the United States were selected due to previous investigations indicating that significant high conductivity flow zones existed in a matrix which include almost no clay content. Data indicated that resistivity corresponded with the fine content in the vadose zone and subsequently corresponds to the saturated hydraulic conductivity. Statistical analysis of resistivity data, and supported by data from the soil sampling and permeameter hydraulic testing, identified isolated high flow regions and zones that can be characterized as broad-scale high hydraulic conductivity features with potentially significant consequences for the migration of water and solutes and therefore are of biogeochemical and ecological significance.}, journal={Journal of Hydrology}, publisher={Elsevier BV}, author={Miller, Ronald B. and Heeren, Derek M. and Fox, Garey A. and Halihan, Todd and Storm, Daniel E. and Mittelstet, Aaron R.}, year={2014}, month={May}, pages={229–240} }
 @inproceedings{akay_özer_fox_2014, title={Use of EPS block geofoam with internal drainage for sandy slopes subjected to seepage flow}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84924942335&partnerID=MN8TOARS}, booktitle={10th International Conference on Geosynthetics, ICG 2014}, author={Akay, O. and Özer, A.T. and Fox, G.A.}, year={2014} }
 @article{white_storm_smolen_busteed_zhang_fox_2014, title={Validation of a Quantitative Phosphorus Loss Assessment Tool}, volume={43}, ISSN={0047-2425}, url={http://dx.doi.org/10.2134/jeq2011.0434}, DOI={10.2134/jeq2011.0434}, abstractNote={Pasture Phosphorus Management Plus (PPM Plus) is a tool that allows nutrient management and conservation planners to evaluate phosphorus (P) loss from agricultural fields. This tool uses a modified version of the widely used Soil and Water Assessment Tool model with a vastly simplified interface. The development of PPM Plus has been fully described in previous publications; in this article we evaluate the accuracy of PPM Plus using 286 field-years of runoff, sediment, and P validation data from runoff studies at various locations in Oklahoma, Texas, Arkansas, and Georgia. Land uses include pasture, small grains, and row crops with rainfall ranging from 630 to 1390 mm yr, with and without animal manure application. PPM Plus explained 68% of the variability in total P loss, 56% of runoff, and 73% of the variability of sediment yield. An empirical model developed from these data using soil test P, total applied P, slope, and precipitation only accounted for 15% of the variability in total P loss, which implies that a process-based model is required to account for the diversity present in these data. PPM Plus is an easy-to-use conservation planning tool for P loss prediction, which, with modification, could be applicable at the regional and national scales.}, number={1}, journal={Journal of Environmental Quality}, publisher={Wiley}, author={White, Michael J. and Storm, Daniel E. and Smolen, Michael D. and Busteed, Philip R. and Zhang, Hailin and Fox, Garey A.}, year={2014}, month={Jan}, pages={224–234} }
 @article{midgley_fox_wilson_felice_heeren_2013, title={<i>In Situ</i> Soil Pipeflow Experiments on Contrasting Streambank Soils}, volume={56}, DOI={10.13031/2013.42685}, abstractNote={Abstract. Soil piping has been attributed as a potential mechanism of instability of embankments and streambanks. Limited field work has been conducted on quantifying and modeling pipeflow and internal erosion processes in the field with either natural or artificially created soil pipes. This research utilized an innovative constant-head trench system to conduct constant-head soil pipe experiments in two contrasting streambanks: Dry Creek in northern Mississippi and Cow Creek in northern Oklahoma. Experiments included open pipes, in which the soil pipe was directly connected to the constant-head trench and open at the streambank face, and clogged pipes, which involved plugging the outlet of the soil pipe using soil excavated adjacent to the pipe. A tensiometer network was used to measure soil water pressures surrounding open and clogged pipe outlets on the streambank face. When pipeflow occurred, flow and sediment samples were collected using flow collection pans to quantify sediment concentrations. Flow and sediment data were used with an existing turbulent pipeflow and internal erosion model to estimate erodibility and critical shear stress properties of the soils, which were subsequently compared to similar properties derived from jet erosion tests. Clogged soil pipes resulted in pore water pressure increases in the soil adjacent to the pipe, which generally remained below saturation during these experimental periods, except at locations close to the plug. Depending on the density of the plugged soil material, the clogged soil pipes either burst, resulting in turbulent pipeflow, or were manually punctured to establish pipeflow. Calibrated critical shear stress from the turbulent pipeflow and internal erosion model matched that observed from jet erosion tests for the less erodible soils on the Dry Creek streambank, where sediment concentrations were consistently below 2 g L -1 even with fairly large hydraulic gradients on the pipe (0.3 m m -1 ). Calibrated erodibility coefficients were much smaller than those measured with jet erosion tests. For the more erodible streambank soils of Cow Creek, sediment concentrations approached 40 g L -1 . There is a need for improved pipeflow modeling that accounts for rapidly changing pipe geometries, partially filled soil pipes, and pipeflow/soil matrix interactions.}, number={2}, journal={Transactions of the ASABE}, publisher={American Society of Agricultural and Biological Engineers (ASABE)}, author={Midgley, Taber L. and Fox, Garey A. and Wilson, Glenn V. and Felice, Rachel and Heeren, Derek}, year={2013}, pages={479–488} }
 @inproceedings{al-madhhachi_fox_hanson_2013, title={A Mechanistic Detachment Rate Model to Predict Soil Erodibility due to Fluvial and Seepage Forces}, ISBN={9780784412947}, url={http://dx.doi.org/10.1061/9780784412947.158}, DOI={10.1061/9780784412947.158}, abstractNote={The erosion rate of cohesive soils is typically computed using an excess shear stress model based on the applied fluvial shear stress. However, no mechanistic approaches are available for incorporating additional forces such as localized groundwater seepage forces into the excess shear stress model parameters. Seepage forces are known to be significant contributors to streambank erosion and failure. The objective of this research was to incorporate seepage forces into a mechanistic fundamental detachment rate model to improve predictions of the erosion rate of cohesive soils. The new detachment model, which is referred to as the "Modified Wilson Model," was based on two modified dimensional soil parameters (b0 and b1) that included seepage forces due to localized groundwater flow gradients. The proposed model provided a general framework for studying the impact of soil properties, fluid characteristics, and seepage forces on cohesive soil erodibility. The proposed model will be described and methods of analysis will be presented for deriving the material parameters from flume tests and jet erosion tests (JETs). To investigate the influence of seepage on erodibility, innovative submerged JETs and larger-scale flume experiments were conducted including cases with and without seepage. Seepage forces influenced the erodibility parameters (b0 and b1) and the corresponding predicted erosion rates. As expected, increased seepage gradients or forces decreased b1 and increased b0 for both flume tests and JETs. The influence of seepage on erosion can be predicted using the "Modified Wilson Model" parameters with a priori flume and/or JET experiments without seepage. Erodibility parameters with or without seepage from flume experiments were statistically equivalent to those derived using JETs. The "Modified Wilson Model" is advantageous in being a more mechanistic, fundamentally based erosion equation that can replace the more commonly used empirical detachment models such as the excess shear stress model.}, booktitle={World Environmental and Water Resources Congress 2013}, publisher={American Society of Civil Engineers}, author={Al-Madhhachi, A. T. and Fox, G. A. and Hanson, G. J.}, year={2013}, month={May}, pages={1608–1618} }
 @article{daly_fox_al-madhhachi_miller_2013, title={A scour depth approach for deriving erodibility parameters from jet erosion tests}, volume={56}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84891467711&partnerID=MN8TOARS}, DOI={10.13031/trans.56.10350}, abstractNote={Abstract. Typically the erosion rate of cohesive soils is modeled using the excess shear stress equation, which includes two soil parameters: the erodibility coefficient (k d ) and the critical shear stress (I„ c ). A jet erosion test (JET) is a standardized method available for deriving the erodibility of cohesive soils. The JET data are typically analyzed using a Blaisdell solution approach. A second solution approach based on direct parameter optimization to the measured scour depth data has recently been proposed but with limited evaluation. Therefore, the objectives of this research were to: (1) develop a new spreadsheet tool that simultaneously solves for the erodibility parameters using both solution approaches, (2) evaluate the solutions in terms of their ability to predict the observed scour depth data, and (3) quantify differences in the predicted erodibility parameters from the two approaches. A series of JETs conducted across the Illinois River watershed in eastern Oklahoma were used to evaluate the performance of the spreadsheet and the solution methodologies. The new scour depth solution provided improved fits to the original scour depth data along with being more stable in converging to a solution as a function of the initial parameter estimates. The automated spreadsheet provides an easy-to-use tool for deriving erodibility parameters from JETs.}, number={6}, journal={Transactions of the ASABE}, author={Daly, E.R. and Fox, G.A. and Al-Madhhachi, A.T. and Miller, R.B.}, year={2013}, pages={1343–1351} }
 @article{fox_al-madhhachi_daly_2013, title={Application of Excess Shear Stress and Mechanistic Detachment Rate Models for the Erodibility of Cohesive Soils}, DOI={10.13031/aim.20131596568}, abstractNote={Abstract. Typically the erosion rate of cohesive soils is modeled using the excess shear stress equation, which includes two soil parameters: the erodibility coefficient (k d ) and the critical shear stress (I„ c ). Alternatively, a mechanistic detachment rate model (“Wilson Model”) was recently developed to predict the erosion rate of cohesive soils. The general framework of the “Wilson Model” was based on two soil parameters: b 0 and b 1 . The “Wilson Model” is advantageous in being a more mechanistic, fundamentally based erosion equation as compared to the more commonly utilized excess shear stress model. The objective of this research was to derive the excess shear stress model parameters (k d and I„ c ) from field jet erosion tests (JETs) on numerous streambanks across the Illinois River watershed to further investigate the erodibility parameters relative to parameter uniformity, correlations between the derived parameters and soil texture, and the applicability of predictive relationships between k d and I„ c . The second objective was to demonstrate the applicability of the “Wilson Model” using field JET data. If a shift to the more fundamentally based “Wilson Model” is expected, similar investigations into parameter uniformity and correlations are needed. This study also investigated correlations between the excess shear stress model parameters, k d and I„ c , and the “Wilson Model” parameters, b 0 and b 1 . A new miniature version of JET device (“mini” JET) was performed on streambanks of varying soil texture within the Illinois River Watershed in northeastern Oklahoma. Soil samples were acquired at locations of the JETs to measure the particle size distribution, average particle size (d 50 ) and bulk density. When considering correlations between the derived parameters and soil texture, no significant relationships existed between k d or I„ c and bulk density, d 50 , percent clay, silt, or sand, or percent clay-silt. Existing empirical relationships should be used with caution considering the variability between the results observed in this research and previous relationships proposed in the literature. Strong correlations were observed between b 0 and k d (R 2 = 0.90) and between b 1 and I„ c (R 2 = 0.93). Therefore, the Wilson Model parameters closely resemble the empirical excess shear stress parameters, but can be mechanistically defined to account for multiple forces acting during the erosion process.}, journal={2013 Kansas City, Missouri, July 21 - July 24, 2013}, publisher={American Society of Agricultural and Biological Engineers}, author={Fox, Garey A and Al-Madhhachi, Abdul-Sahib and Daly, Erin R}, year={2013} }
 @inproceedings{daly_fox_al-madhhachi_2013, title={Application of excess shear stress and mechanistic detachment rate models for the erodibility of cohesive soils}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84881643806&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2013, ASABE 2013}, author={Daly, E.R. and Fox, G.A. and Al-Madhhachi, A.-S.T.}, year={2013}, pages={2540–2550} }
 @inproceedings{penn_heeren_fox_2013, place={St. Joseph, Michigan}, title={Application of isothermal calorimetry to the study of phosphorus sorption onto soils in a flow-through system}, DOI={10.13031/aim.20131621201}, abstractNote={Abstract. The degree, mechanisms, and kinetics of phosphorus (P) sorption onto soils can have a significant influence on leaching losses of P from soil. The objectives of this study were to measure the impact of retention time (RT) on P sorption in a flow-through system intended to simulate downward movement of a P solution through two different riparian soils, and determine if isothermal titration calorimetry (ITC) can provide useful information reflective of flow-through results. Topsoil from two riparian/alluvial soils was sampled and characterized for P concentrations and parameters related to P sorption. Flow-through P sorption experiments were conducted in order to examine the effect of RT and inflow P concentration on P sorption; this was compared to results of ITC experiments where the heat of reaction was measured with the addition of P to soils. Results of ITC experiments were reflective of both soil characterization and flow-through sorption in that the Barren Fork soil sorbed less P, but at a faster rate, compared to Clear Creek. Based on thermograms, the dominant P sorption reaction was ligand exchange onto Al/Fe oxides/hydroxides, with a lesser degree of precipitation. Phosphorus removal for both soils was limited by physical nonequilibrium instead of chemical nonequilibrium (sorption kinetics). For the Clear Creek soil, the ITC analysis illustrated that P sorption was limited more by physical diffusion of P through micropores to sorption sites rather than chemical kinetics. For the Barren Fork soil, results indicated that the limiting process was pore scale transport from bulk flow to sorption sites, which was a function of flow rate. The calorimetry approach presented can help provide soil-specific information on the risk of P inputs to leaching (degree of P sorption) under different conditions (flow rate or RT), and potential for desorption (P sorption mechanisms).}, number={131621201131621201}, booktitle={2013 Kansas City, Missouri, July 21 - July 24, 2013}, publisher={American Society of Agricultural and Biological Engineers}, author={Penn, C.J. and Heeren, D.M. and Fox, G.A.}, year={2013} }
 @inproceedings{penn_hereen_fox_2013, title={Application of isothermal calorimetry to the study of phosphorus sorption onto soils in a flow-through system}, volume={6}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84881624253&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2013, ASABE 2013}, author={Penn, C.J. and Hereen, D.M. and Fox, G.A.}, year={2013}, pages={4963–4976} }
 @article{fox_felice_2013, title={Bank undercutting and tension failure by groundwater seepage: predicting failure mechanisms}, volume={39}, ISSN={0197-9337}, url={http://dx.doi.org/10.1002/esp.3481}, DOI={10.1002/esp.3481}, abstractNote={ABSTRACT}, number={6}, journal={Earth Surface Processes and Landforms}, publisher={Wiley}, author={Fox, Garey A. and Felice, Rachel G.}, year={2013}, month={Oct}, pages={758–765} }
 @article{akay_özer_fox_bartlett_arellano_2013, title={Behavior of sandy slopes remediated by EPS-block geofoam under seepage flow}, volume={37}, ISSN={0266-1144}, url={http://dx.doi.org/10.1016/j.geotexmem.2013.02.005}, DOI={10.1016/j.geotexmem.2013.02.005}, abstractNote={Expanded polystyrene (EPS) geofoam (geofoam block) is commonly used as a lightweight fill for many civil engineering applications. However, when used for slope remediation, the behavior of geofoam block for slope systems undergoing seepage flow is not well known. In this study, a total of 36 laboratory lysimeter experiments (dimensions of 60 cm height, 20 cm width, and 200 cm length) were conducted to investigate the behavior of sandy slopes containing geofoam blocks as a lightweight fill material. These experiments were conducted with three different values of constant water pressure in the water reservoir located at one end of the lysimeter. In addition, three different configurations of geofoam block were tested with geofoam blocks placed on the face of the packed sandy slope. The dimensions of the geofoam blocks were 2.5 cm high, 5 cm wide, and 15 cm long to achieve a 1:20 scale corresponding to actual block size that is commonly manufactured. Laboratory physical test results were quantified by coupled seepage flow and slope stability models showing the adverse effect of seepage on the factor of safety (FS). Geofoam block configurations were found to be stable against seepage conditions which would cause a shallow-seated failure of the slope in the absence of the geofoam blocks. This is due to the fact that the geofoam blocks could completely fill the mass of the existing slope material subjected to failure. However, the geofoam block configurations were unstable against seepage conditions that resulted in deep-seated failures of marginally stable, sand slopes.}, journal={Geotextiles and Geomembranes}, publisher={Elsevier BV}, author={Akay, Onur and Özer, A. Tolga and Fox, Garey A. and Bartlett, Steven F. and Arellano, David}, year={2013}, month={Apr}, pages={81–98} }
 @article{al-madhhachi_hanson_fox_tyagi_bulut_2013, title={Deriving Parameters of a Fundamental Detachment Model for Cohesive Soils from Flume and Jet Erosion Tests}, volume={56}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84878551266&partnerID=MN8TOARS}, DOI={10.13031/2013.42669}, abstractNote={Abstract. The erosion rate of cohesive soils is commonly quantified using the excess shear stress model, which is dependent on two major soil parameters: the critical shear stress (I„ c ) and the erodibility coefficient (k d ). A submerged jet test (jet erosion test, or JET) is one method that has been developed for measuring these parameters. The disadvantage of using the excess shear stress model is that parameters I„ c and k d change according to erosion conditions, such as soil structure, soil orientation, type of clay, presence of roots, and seepage forces. A more mechanistically based detachment model, called the Wilson model, is proposed in this article for modeling the erosion rate of soils using hydraulic analysis of a JET. The general framework of the Wilson model is based on two soil parameters (b 0 and b 1 ). The objectives of this study were to: (1) develop methods of analysis of the JET to determine parameters b 0 and b 1 for the Wilson model in a similar fashion to the previous methodology developed for open-channel flow, and (2) compare the excess stress model parameter (k d ) and the Wilson model parameters (b 0 and b 1 ) determined from the flume tests and JETs for two cohesive soils. Flume tests, treated as the standard test method, and original and “mini” JETs were conducted on two soils to independently measure the excess shear stress model parameter (k d ) and the Wilson model parameters (b 0 and b 1 ). Soil samples of two cohesive soils (silty sand and clayey sand soils) were packed in a soil box for the flume tests and the JETs at water contents ranging from 8.7% to 18.1%. No statistically significant differences were observed for the excess shear stress model parameter (k d ) and for the Wilson model parameters (b 0 and b 1 ) when determined from the flume tests and JET devices, except for b 1 with the original JET. The Wilson model is advantageous in being a more mechanistic, fundamentally based erosion equation as compared to the excess shear stress model. The Wilson model can be used in place of the excess shear stress model with parameters that can be estimated using existing JET techniques.}, number={2}, journal={Transactions of the ASABE}, publisher={American Society of Agricultural and Biological Engineers (ASABE)}, author={Al-Madhhachi, Abdul-Sahib T. and Hanson, Gregory J. and Fox, Garey A. and Tyagi, Avdhesh K. and Bulut, Rifat}, year={2013}, pages={489–504} }
 @article{sabbagh_muñoz-carpena_fox_2013, title={Distinct influence of filter strips on acute and chronic pesticide aquatic environmental exposure assessments across U.S. EPA scenarios}, volume={90}, ISSN={0045-6535}, url={http://dx.doi.org/10.1016/j.chemosphere.2012.06.034}, DOI={10.1016/j.chemosphere.2012.06.034}, abstractNote={Vegetative filter strips (VFS) are proposed for protection of receiving water bodies and aquatic organisms from pesticides in runoff, but there is debate regarding the efficiency and filter size requirements. This debate is largely due to the belief that no quantitative methodology exists for predicting runoff buffer efficiency when conducting acute and/or chronic environmental exposure assessments. Previous research has proposed a modeling approach that links the U.S. Environmental Protection Agency's (EPA's) PRZM/EXAMS with a well-tested process-based model for VFS (VFSMOD). In this research, we apply the modeling framework to determine (1) the most important input factors for quantifying mass reductions of pesticides by VFS in aquatic exposure assessments relative to three distinct U.S. EPA scenarios encompassing a wide range of conditions; (2) the expected range in percent reductions in acute and chronic estimated environmental concentrations (EECs); and (3) the differential influence of VFS when conducting acute versus chronic exposure assessments. This research utilized three, 30-yr U.S. EPA scenarios: Illinois corn, California tomato, and Oregon wheat. A global sensitivity analysis (GSA) method identified the most important input factors based on discrete uniform probability distributions for five input factors: VFS length (VL), organic-carbon sorption coefficient (K(oc)), half-lives in both water and soil phases, and application timing. For percent reductions in acute and chronic EECs, VL and application timing were consistently the most important input factors independent of EPA scenario. The potential ranges in acute and chronic EECs varied as a function of EPA scenario and application timing. Reductions in acute EECs were typically less than percent reductions in chronic EECs because acute exposure was driven primarily by large individual rainfall and runon events. Importantly, generic specification of VFS design characteristics equal across scenarios should be avoided. The revised pesticide assessment modeling framework offers the ability to elucidate the complex and non-linear relationships that can inform targeted VFS design specifications.}, number={2}, journal={Chemosphere}, publisher={Elsevier BV}, author={Sabbagh, George J. and Muñoz-Carpena, Rafael and Fox, Garey A.}, year={2013}, month={Jan}, pages={195–202} }
 @article{heeren_fox_fox_storm_miller_mittelstet_2013, title={Divergence and flow direction as indicators of subsurface heterogeneity and stage-dependent storage in alluvial floodplains}, volume={28}, ISSN={0885-6087}, url={http://dx.doi.org/10.1002/hyp.9674}, DOI={10.1002/hyp.9674}, abstractNote={Assuming homogeneity in alluvial aquifers is convenient, but limits our ability to accurately predict stream‐aquifer interactions. Research is needed on (i) identifying the presence of focused, as opposed to diffuse, groundwater discharge/recharge to streams and (ii) the magnitude and role of large‐scale bank and transient storage in alluvial floodplains relative to changes in stream stage. The objective of this research was to document and quantify the effect of stage‐dependent aquifer heterogeneity and bank storage relative to changes in stream stage using groundwater flow divergence and direction. Monitoring was performed in alluvial floodplains adjacent to the Barren Fork Creek and Honey Creek in northeastern Oklahoma. Based on results from subsurface electrical resistivity mapping, observation wells were installed in high and low electrical resistivity subsoils. Water levels in the wells were recorded real time using pressure transducers (August to October 2009). Divergence was used to quantify heterogeneity (i.e. variation in hydraulic conductivity, porosity, and/or aquifer thickness), and flow direction was used to assess the potential for large‐scale (100 m) bank or transient storage. Areas of localized heterogeneity appeared to act as divergence zones allowing stream water to quickly enter the groundwater system, or as flow convergence zones draining a large groundwater area. Maximum divergence or convergence occurred with maximum rates of change in flow rates or stream stage. Flow directions in the groundwater changed considerably between base and high flows, suggesting that the floodplains acted as large‐scale bank storage zones, rapidly storing and releasing water during passage of a storm hydrograph. During storm events at both sites, the average groundwater direction changed by at least 90° from the average groundwater direction during baseflow. Aquifer heterogeneity in floodplains yields hyporheic flows that are more responsive and spatially and temporally complex than would be expected compared to more common assumptions of homogeneity. Copyright © 2012 John Wiley & Sons, Ltd.}, number={3}, journal={Hydrological Processes}, publisher={Wiley}, author={Heeren, D. M. and Fox, G. A. and Fox, A. K. and Storm, D. E. and Miller, R. B. and Mittelstet, A. R.}, year={2013}, month={Jan}, pages={1307–1317} }
 @article{fox_penn_2013, title={Empirical model for quantifying total phosphorus reduction by vegetative filter strips}, volume={56}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84885461477&partnerID=MN8TOARS}, DOI={10.13031/trans.56.100133}, number={4}, journal={Transactions of the ASABE}, author={Fox, G.A. and Penn, C.J.}, year={2013}, pages={1461–1469} }
 @inproceedings{daly_storm_fox_langendoen_2013, place={St. Joseph, Michigan}, title={Evaluation of the Conservational Channel Evolution and Pollutant Transport System (CONCEPTS) Applied to Composite Streambanks in the Ozark Highlands Ecoregion}, url={http://dx.doi.org/10.13031/aim.20131620552}, DOI={10.13031/aim.20131620552}, abstractNote={Abstract. Hydraulic models are often employed to predict the response of a stream to a proposed restoration design. The shortfall of many currently used models is that they only look at the site where stabilization will occur without considering upstream and downstream effects. The one-dimensional (1D) computer model Conservational Channel Evolution and Pollutant Transport System (CONCEPTS) addresses this shortcoming by modeling streambank stabilization on a reach scale. The capability of this model is attractive to basin managers; however, CONCEPTS is still an emerging model and has not been applied to a wide variety of composite streambanks. The objectives of this study were to perform an evaluation of the Conservational Channel Evolution and Pollutant Transport System (CONCEPTS) applied to composite streambanks in the Ozark Highlands ecoregion, and to demonstrate CONCEPTS’s ability to predict the long-term stability of streambank stabilization. CONCEPTS was used to simulate a 9.25 km reach along the Barren Fork Creek in northeastern Oklahoma. A sensitivity analysis was first performed to identify input parameters with the greatest effect on bank erosion predictions in CONCEPTS. Model results were most sensitive to (1) the correction factor that accounts for increased shear stresses in a meandering stream that cannot be simulated by 1D models and (2) the internal angle of friction of the bank soils followed by the critical shear stress, effective cohesion, erodibility coefficient and the permeability. Next, CONCEPTS was calibrated using ground-based and aerial bank retreat measurements to produce realistic predictions. Model calibration was conducted by reducing the critical shear stress of the noncohesive soils until the predicted retreat matched the observed data. Using the calibrated model, two streambank stabilization techniques were simulated at two highly unstable cross sections. Fluvial erosion was reduced by simulating the application of riprap at the bank toe, and geotechnical failure was reduced by simulating a slope stabilization technique. In general, CONCEPTS predicted a high percent reduction of cumulative fines yield, bank retreat at the bank top and toe, and cumulative change in thalweg elevation for both stabilization techniques. Due to CONCEPTS limitations, a two or three-dimensional model may be needed to perform a comprehensive analysis of streambank stability for the composite streambanks in the Ozark Highlands ecoregion. Additional research is needed on the use of the internal angle of friction as a lumped calibration parameter for cohesionless soils. However, with the proper calibration and caution, CONCEPTS is a useful tool to guide the design and prioritization of streambank stabilization projects.}, number={131620552131620552}, publisher={American Society of Agricultural and Biological Engineers}, author={Daly, Erin R and Storm, Daniel E and Fox, Garey A and Langendoen, Eddy J}, year={2013} }
 @article{freiberger_heeren_fox_2013, title={Finite element modeling of phosphorus leaching through floodplain soils dominated by preferential flow pathways}, DOI={10.13031/aim.20131583250}, abstractNote={Abstract. Phosphorus is a critical nutrient in soils, providing both positive and negative effects to different systems. While optimum crop growth requires a range of P above 0.2 mg/L, preventing surface water enrichment generally requires P to be below 0.03 mg/L. Proper application and control of phosphorus is important to increase farming efficiency and to protect freshwater systems from toxic algal growth. While the movement of phosphorus through many soil types has been well-documented, the presence of highly conductive, gravel outcrops and macropores in soil can have a significant, poorly-documented effect on phosphorus movement. In the Ozark ecoregion, for example, the erosion of carbonate bedrock (primarily limestone) by slightly acidic water has left a large residuum of chert gravel in Ozark soils, with floodplains generally consisting of coarse chert gravel overlain by a mantle (1 to 300 cm) of gravelly loam or silt loam. Highly conductive gravel outcrops and macropores may create preferential flow pathways for water moving through the soil column, along with any solutes in solution. In previous research, floodplain sites in Oklahoma and Arkansas were chosen due to the presence of cherty gravel outcrops that reached near the soil surface. Soil properties were evaluated, and two-dimensional electrical resistivity data were collected and correlated to hydraulic conductivity. Water was then applied to several plots (1, 10, and 100 m 2 ) with known concentrations of phosphorus, Rhodamine WT, and chloride for up to 52 hours, and flow towards a nearby stream was monitored with observation wells. The objective of this research was to use finite element modeling to develop a long-term model for this phenomenon for future predictions. Results from the previous research were modeled with HYDRUS-3D, a three-dimensional, finite-element model for flow and contaminant transport (both equilibrium and physical/chemical nonequilibrium transport) through soils. HYDRUS-3D was setup to simulate the 1 m 2 infiltration plot at the Barren Fork Creek site, with initial hydraulic conductivity data calculated from the plot scale infiltration experiment for the upper silt loam soil and from 2D geophysical data for the underlying gravel. The mobile-immobile (MIM) phase model within HYDRUS was also utilized, and MIM solute transport parameters were found iteratively using chloride tracer data taken from two wells. Results from this research will be used to predict phosphorus transport parameters and solve for long-term phosphorus transport through these soil profiles.}, journal={2013 Kansas City, Missouri, July 21 - July 24, 2013}, publisher={American Society of Agricultural and Biological Engineers}, author={Freiberger, Ryan P and Heeren, Derek M. and Fox, Garey A.}, year={2013} }
 @inproceedings{freiberger_heeren_fox_2013, title={Finite element modeling of phosphorus leaching through floodplain soils dominated by preferential flow pathways}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84881642124&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2013, ASABE 2013}, author={Freiberger, R.P. and Heeren, D.M. and Fox, G.A.}, year={2013}, pages={340–348} }
 @article{criswell_fox_miller_daly_al-madhhachi_2013, title={Flume Experiments to Determine the Erodibility of Gravel Streambank Soils}, DOI={10.13031/aim.20131620973}, abstractNote={Abstract. Fluvial erosion in streambank stability models is typically modeled using an excess shear stress equation based on two soil parameters: the erodibility coefficient (k d ) and critical shear stress (I„ c ). For cohesive soils, methods exist such as jet erosion tests (JETs) for measuring k d and I„ c . For noncohesive bank materials such as sands and gravels, I„ c is commonly estimated using the Shields diagram based on the median particle diameter. However, no universally accepted relationship exists for estimating k d for noncohesive soils. Also, recent research has proposed the use of more fundamentally-based mechanistic detachment models in place of the excess shear stress equation, but limited research has been performed in deriving the parameters of these alternative detachment models. One such model investigated in this research is the Wilson Model, which is based on two parameters: b 0 and b 1 . The objectives of this research included the following: (i) conduct flume experiments on noncohesive gravels to quantify detachment rates relative to the imposed shear stress, (ii) derive k d and I„ c and b 0 and b 1 for these gravels, (iii) determine if relationships can be developed relating k d versus I„ c and b 0 versus b 1 , (iv) compare the k d -I„ c relationship to previously proposed relationships, and (v) compare the relative performance of the models in being able to fit the scour data. Flume experiments were conducted at the USDA-ARS Hydraulics Laboratory. Samples of gravels were extracted from streambanks on the Barren Fork Creek in eastern Oklahoma. The samples were sieved into particle size classes and then at least triplicate flume experiments were performed with average gravel sizes of 0.45, 0.60, 1.30, and 1.90 cm (0.18, 0.25, 0.50, and 0.75 inches, respectively). Scour depth was measured using a point gage during the flume experiment. The k d -I„ c relationships derived from the laboratory experiments followed a power law relationship with the form: k d =2.23I„ c -0.50 (R 2 = 0.65). The Wilson Model parameters b 0 and b 1 derived from this research appeared to have a similar relationship but different magnitude than k d and I„ c . The k d -I„ c or b 0 -b 1 relationships can be used to model fluvial erosion of the noncohesive gravel and therefore the resulting streambank failure of composite banks.}, journal={2013 Kansas City, Missouri, July 21 - July 24, 2013}, publisher={American Society of Agricultural and Biological Engineers}, author={Criswell, David T and Fox, Garey A and Miller, Ron B and Daly, Erin and Al-Madhhachi, Abdul-Sahib}, year={2013} }
 @inproceedings{criswell_fox_al-madhhachi_miller_daly_2013, title={Flume experiments to determine the erodibility of gravel streambank soils}, volume={6}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84881625740&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2013, ASABE 2013}, author={Criswell, D.T. and Fox, G.A. and Al-Madhhachi, A.-S.T. and Miller, R. and Daly, E.}, year={2013}, pages={4913–4923} }
 @article{tilak_ojewole_williford_fox_sobecki_larson_2013, title={Formation of Manganese Oxide Coatings onto Sand for Adsorption of Trace Metals from Groundwater}, volume={42}, ISSN={0047-2425}, url={http://dx.doi.org/10.2134/jeq2013.04.0142}, DOI={10.2134/jeq2013.04.0142}, abstractNote={Manganese oxide (MnO) occurs naturally in soil and has a high affinity for trace metals adsorption. In this work, we quantified the factors (pH; flow rate; use of oxidants such as bleach, HO, and O; initial Mn(II) concentrations; and two types of geologic media) affecting MnO coatings onto Ottawa and aquifer sand using batch and column experiments. The batch experiments consisted of manual and automated titration, and the column experiments mimicked natural MnO adsorption and oxidation cycles as a strategy for in situ adsorption. A Pb solution of 50 mg L was passed through MnO-coated sand at a flow rate of 4 mL min to determine its adsorption capacity. Batch experimental results showed that MnO coatings increased from pH 6 to 8, with maximum MnO coating occurring at pH 8. Regarding MnO coatings, bleach and O were highly effective compared with HO. The Ottawa sand had approximately twice the MnO coating of aquifer sand. The sequential increase in initial Mn(II) concentrations on both sands resulted in incremental buildup of MnO. The automated procedure enhanced MnO coatings by 3.5 times compared with manual batch experiments. Column results showed that MnO coatings were highly dependent on initial Mn(II) and oxidant concentrations, pH, flow rate, number of cycles (h), and the type of geologic media used. Manganese oxide coating exceeded 1700 mg kg for Ottawa sand and 130 mg kg for aquifer sand. The Pb adsorption exceeded 2200 mg kg for the Ottawa sand and 300 mg kg for the aquifer sand.}, number={6}, journal={Journal of Environmental Quality}, publisher={Wiley}, author={Tilak, A. S. and Ojewole, S. and Williford, C. W. and Fox, G. A. and Sobecki, T. M. and Larson, S. L.}, year={2013}, month={Nov}, pages={1743–1751} }
 @article{heeren_fox_storm_haggard_penn_halihan_2013, title={Impact of Measurement Scale on Infiltration and Phosphorus Leaching in Ozark Floodplains}, DOI={10.13031/aim.20131621213}, abstractNote={Abstract. Increased nutrient loads have resulted in several adverse impacts on surface water quality, including excessive algal growth, fish kills, and drinking water taste and odor issues across the United States and especially in the Ozark ecoregion of northeastern Oklahoma and northwestern Arkansas. The significance of this problem has been highlighted by litigation, with one case even reaching the U.S. Supreme Court (Arkansas et al. v. Oklahoma et al., 503 U.S. 91) which required the upstream state to meet downstream water quality standards. The overarching objective of this line of research was to characterize phosphorus leaching to alluvial aquifers in the coarse gravel floodplains of the Ozark ecoregion, while the specific objective of this paper was to quantify infiltration and hydraulic conductivity across a range of scales (point to 100 m 2 ) to evaluate the effect of the scale of measurement. It is hypothesized that hydrologic heterogeneities (e.g., macropores and gravel outcrops) in the subsurface play an integral role in impacting flow and contaminant transport between the soil surface and alluvial aquifers. Innovative field studies, including plot scale injection experiments, were performed across a range of soil types at each of three floodplain sites in the Ozark ecoregion. Solutes in the injection water included phosphorus, P (highly sorptive), Rhodamine WT (slightly sorptive), and chloride (conservative). Plots maintained a constant head of 2 to 9 cm for up to 52 hours. Effective saturated hydraulic conductivity (K eff ) data, based on plot scale infiltration rates, were high (0.6 to 68 cm hr -1 ) and varied greatly, even within a single floodplain. The K eff was also measured with a double ring infiltrometer and estimated at the point scale using Retention Curve (RETC) along with particle size distribution data. Point scale estimates were significantly lower than plot scale K eff , and also failed to capture the variability of K eff within a field site. The estimated permeability of the limiting layer reported by the U.S. Natural Resources Conservation Service (NRCS) Soil Survey was consistent with point scale estimates of K eff , but was lower than plot scale K eff at most sites. Plot scale infiltration tests are recommended over double ring infiltrometer tests or point scale estimates, although only small plots (1 m by 1 m) are necessary.}, journal={2013 Kansas City, Missouri, July 21 - July 24, 2013}, publisher={American Society of Agricultural and Biological Engineers}, author={Heeren, Derek M. and Fox, Garey A. and Storm, Daniel E. and Haggard, Brian E. and Penn, Chad J. and Halihan, Todd}, year={2013} }
 @inproceedings{heeren_fox_storm_haggard_penn_halihan_2013, title={Impact of measurement scale on infiltration and phosphorus leaching in Ozark floodplains}, volume={6}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84881628532&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2013, ASABE 2013}, author={Heeren, D.M. and Fox, G.A. and Storm, D.E. and Haggard, B.E. and Penn, C.J. and Halihan, T.}, year={2013}, pages={4991–5006} }
 @article{midgley_fox_wilson_felice_heeren_2013, title={In situ soil pipeflow experiments on contrasting streambank soils}, volume={56}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84878571859&partnerID=MN8TOARS}, number={2}, journal={Transactions of the ASABE}, author={Midgley, T.L. and Fox, G.A. and Wilson, G.V. and Felice, R.M. and Heeren, D.M.}, year={2013}, pages={479–488} }
 @article{wilson_nieber_sidle_fox_2013, title={Internal Erosion during Soil Pipeflow: State of the Science for Experimental and Numerical Analysis}, volume={56}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84878537147&partnerID=MN8TOARS}, DOI={10.13031/2013.42667}, abstractNote={Keywords: Ephemeral gully erosion Erodibility Internal erosion Landslides Pipeflow Soil pipes. Abstract. Many field observations have led to speculation on the role of piping in embankment failures, landslides, and gully erosion. However, there has not been a consensus on the subsurface flow and erosion processes involved, and inconsistent use of terms have exacerbated the problem. One such piping process that has been the focus in numerous field observations, but with very limited mechanistic experimental work, is flow through a discrete macropore or soil pipe. Questions exist as to the conditions under which preferential flow through soil pipes results in internal erosion, stabilizes hillslopes by acting as drains, destabilizes hillslopes via pore-pressure buildups, and results in gully formation or reformation of filled-in ephemeral gullies. The objectives of this article are to review discrepancies in terminology in order to represent the piping processes better, to highlight past experimental work on the specific processes of soil pipeflow and internal erosion, and to assess the state-of-the-art modeling of pipeflow and internal erosion. The studies reviewed include those that examined the process of slope stability as affected by the clogging of soil pipes, the process of gullies forming due to mass failures caused by flow into discontinuous soil pipes, and the process of gully initiation by tunnel collapse due to pipes enlarging by internal erosion. In some of these studies, the soil pipes were simulated with perforated tubes placed in the soil, while in others the soil pipes were formed from the soil itself. Analytical solutions of the excess shear stress equation have been applied to experimental data of internal erosion of soil pipes to calculate critical shear stress and erodibility properties of soils. The most common numerical models for pipeflow have been based on Richards’ equation, with the soil pipe treated as a highly conductive porous medium instead of a void. Incorporating internal erosion into such models has proven complicated due to enlargement of the pipe with time, turbulent flow, and episodic clogging of soil pipes. These studies and modeling approaches are described, and gaps in our understanding of pipeflow and internal erosion processes and our ability to model these processes are identified, along with recommendations for future research.}, number={2}, journal={Transactions of the ASABE}, publisher={American Society of Agricultural and Biological Engineers (ASABE)}, author={Wilson, Glenn V. and Nieber, John L. and Sidle, Roy C. and Fox, Garey A.}, year={2013}, pages={465–478} }
 @article{al-madhhachi_hanson_fox_tyagi_bulut_2013, title={Measuring soil erodibility using a laboratory "mini" jet}, volume={56}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84884175110&partnerID=MN8TOARS}, DOI={10.13031/trans.56.9742}, abstractNote={Abstract. Typically soil erodibility is quantified using an excess shear stress equation, dependent on two major soil parameters: the critical shear stress (I„ c ) and the erodibility coefficient (k d ). A submerged jet test (JET, Jet Erosion Test) is one method that has been developed and methodology of use established in the literature for measuring these parameters. In this study, a new miniature version of the JET device (“mini” JET), with the advantage of being easier to use in the field, was used to measure I„ c and k d for two soils (silty sand and clayey sand), and results were compared to the larger original laboratory JET. The objective of this research was to determine if the “mini” JET measured equivalent values for I„ c and k d compared to the original JET device. In-order to compare the performance and repeatability of both JET devices, tests were performed on paired samples prepared in the same way and tested at the same time. Samples of the soils tested were prepared at different water contents with a standard compaction effort of 600 kN-m/m 3 (ASTM). Some variability in measuring I„ c and k d was observed between paired samples due to variability in the soil texture of the soil samples and differences in soil moisture levels. The k d values measured by the two JET devices for both soils were not significantly different. The I„ c values measured by the “mini” JET were consistently lower than those measured by the original JET. This was hypothesized to be due to the structure of the soil sample due to the compaction method and the procedure utilized to determine I„ c . Adjustment of the equilibrium depth of the “mini” JET resulted in small differences in the estimated I„ c between both JET devices. Both JET devices also demonstrated consistent performance in measuring I„ c -k d relationships, which were compared with those observed in previous field research.}, number={3}, journal={Transactions of the ASABE}, author={Al-Madhhachi, A.T. and Hanson, G.J. and Fox, G.A. and Tyagi, A.K. and Bulut, R.}, year={2013}, pages={901–910} }
 @article{al-madhhachi_fox_2013, title={Modified Excess Shear Stress Model Parameters based on Mechanistic Predictions from a Detachment Rate Model}, DOI={10.13031/aim.20131596581}, abstractNote={Abstract. The excess shear stress approach is commonly used to quantify the erosion rate of cohesive soils due to fluvial forces, dependent on two major soil parameters: the critical shear stress (I„ c ) and the erodibility coefficient (k d ). The excess shear stress equation is commonly used in streambank, hillslope, and runoff models. However, mechanistic approaches are currently unavailable for incorporating multiple forces, such as localized groundwater seepage, into these parameters. A more mechanistically-based detachment model, the “Modified Wilson Model,” was recently developed based on two soil parameters (b 0 and b 1 ) for modeling the erosion rate of soils using the hydraulic analysis of an open channel or a jet erosion test (JET). The objective of this study was to mathematically derive relationships for modifying the excess shear stress parameters (I„ c and k d ) based on parameter predictions by the mechanistic detachment rate model (b 0 and b 1 ). Therefore, a more mechanistic determination of erodibility parameters can be achieved without altering the structure of many sediment transport models constructed on the basis of the excess shear stress approach. Expressions for the modified I„ c and k d were based on equating two detachment rate models and assuming that the power term in the excess shear stress equation was 0.5. Data from previous laboratory and in-situ JET devices and flume tests performed on two cohesive soils (silty sand and clayey sand) for a case with a single force (fluvial only) and a case with multiple forces (fluvial and seepage) were utilized to derive the original excess stress model parameters along with the modified I„ c and k d parameters. The modified parameters in the excess shear stress equation allowed improved predictions of the observed data for both the flume tests and JETs.}, journal={2013 Kansas City, Missouri, July 21 - July 24, 2013}, publisher={American Society of Agricultural and Biological Engineers}, author={Al-Madhhachi, Abdul-Sahib T and Fox, Garey A}, year={2013} }
 @inproceedings{al-madhhachi_fox_2013, title={Modified excess shear stress model parameters based on mechanistic predictions from a detachment rate model}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84881650740&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2013, ASABE 2013}, author={Al-Madhhachi, A.-S.T. and Fox, G.A.}, year={2013}, pages={2565–2583} }
 @article{wilson_fox_2013, title={Pore-water pressures associated with clogging of soil pipes: Numerical analysis of laboratory experiments}, volume={77}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84880722808&partnerID=MN8TOARS}, DOI={10.2136/sssaj2012.0416}, abstractNote={Clogging of soil pipes due to excessive internal erosion has been hypothesized to cause extreme erosion events such as landslides, debris flows, and gullies, but confirmation of this phenomenon has been lacking. Laboratory and field measurements have failed to measure pore‐water pressures within pipes and models of pipe flow have not addressed internal erosion or pipe clogging. The objective of this study was to model laboratory experiments of pipe flow in which clogging was observed in order to understand the clogging process. Richards' equation was used to model pipe flow, with the soil pipe represented as a highly conductive, low‐retention porous medium. The modeling used two contrasting boundary conditions, constant flux (CF) and constant head (CH), to quantify pressure buildups due to pipe clogging and differences in simulated pressures between the two imposed boundary conditions. Unique to these simulations was inclusion of pipe enlargement with time due to internal erosion, representation of partially full flow conditions, and inclusion of pipe clogging. Both CF and CH boundary conditions confirmed the concept of pressure buildup as a result of pipe clogging. Pressure jumps of around 54 m for CF and 18 cm for CH occurred in <0.1 s, while soil water pressures 4 cm radially outward from the pipe had not responded. These findings demonstrate the need to measure pressures within soil pipes due to hydraulic nonequilibrium between the pipe and soil matrix. Pore water pressures within the pipe below the clog rapidly (<0.25 s) drained to unsaturated conditions, indicating the ability of soil pipes to drain hillslopes and rapidly recover when clogs are flushed from the soil pipe. These dynamic processes need to be incorporated into stability models to properly model hillslope processes.}, number={4}, journal={Soil Science Society of America Journal}, author={Wilson, G.V. and Fox, G.A.}, year={2013}, pages={1168–1181} }
 @inproceedings{lovern_fox_miller_2013, title={Quantifying the Erodibility and Geotechnical Strength of Cohesive Alluvial Soils Following Streambank Reconstruction}, ISBN={9780784412947}, url={http://dx.doi.org/10.1061/9780784412947.196}, DOI={10.1061/9780784412947.196}, abstractNote={Post-construction data following streambank restoration and stabilization projects are currently lacking relative to the resistance of cohesive streambanks to geotechnical failure and fluvial erosion. This research sought to quantify differences in erodibility and geotechnical properties of natural and restored banks after construction. The streambank environments varied with respect to the presence/type of construction and resulting bank slopes. Streambank conditions included modified fill bank plots, modified cut bank plots, and non-modified control bank plots. Geotechnical resistance to failure was quantified using the Iowa borehole shear test (BST) to measure the in-situ drained shear strength of soils. Fluvial resistance to erosion was measured using an in-situ “mini” jet erosion test (“mini” JET) to estimate the erodibility coefficient and critical shear stress. Bulk densities were impacted by construction activities with a general trend towards higher bulk densities with greater construction modification. Geotechnical strength, in terms of the soil’s effective cohesion for the modified fill bank plots, differed between the modified cut bank plots and the non-modified control plots but additional samples are needed for statistical relevance. Surprisingly, fluvial resistance to erosion may not be influenced by streambank modification based on “mini” JETs conducted to date. Variability in fluvial resistance parameters within each treatment was as large as differences between treatments. These modifications to the streambank fluvial and geotechnical resistance properties should be considered when modeling the impact of stabilization practices on streambanks.}, booktitle={World Environmental and Water Resources Congress 2013}, publisher={American Society of Civil Engineers}, author={Lovern, S. B. and Fox, G. A. and Miller, R. B.}, year={2013}, month={May}, pages={2000–2008} }
 @article{fox_miller_lovern_purvis_penn_2013, title={Sediment and Phosphorus Loading from Protected and Unprotected Streambanks in Eastern Oklahoma}, DOI={10.13031/aim.20131596591}, abstractNote={Abstract. Nutrients and excessive sediment are two main nonpoint source pollutants in the United States. In some watersheds, the majority of the total sediment load to streams and rivers is from streambank erosion. The presence of riparian vegetation can significantly decrease streambank erosion in some locations. Streambank erosion and failure may be one pathway for phosphorus (P) loading to streams, but insufficient data exists on actual loading from this source and the potential protective effect of riparian vegetation in most watersheds. The objective of this research was to characterize the distribution of soil phosphorus concentrations in streambanks both with and without implemented riparian protection in the Barren Fork Creek watershed in eastern Oklahoma and to estimate P loading due to bank erosion. Barren Fork Creek is a state-designated Scenic River in Oklahoma where soil phosphorus (P) levels are potentially high due to historic poultry litter application. Streambank soil samples were collected at three transects and at four vertical locations at six different reaches. The core samples were collected up to 50 cm into the bank at each location, and were analyzed for water-soluble phosphorus (WSP), pH, and electrical conductivity (EC). Contour plots of streambank phosphorus concentrations illustrated considerable differences among reaches relative to adjacent land use. Lateral bank erosion over a seven year period (2003-2010) was estimated using NAIP aerial imagery. Average streambank migration rates were approximately 8 m for the three sites with riparian protection compared to 45 m for the three sites without riparian protection over the seven year period. A helicopter video reconnaissance of the Barren Fork Creek watershed in Oklahoma estimated the percent of the banks that were failing to be approximately 38% of the total length (considering left and right banks). Consequently, streambank erosion represents a significant source of phosphorus entering Barren Fork Creek and eventually impacting water supply reservoirs. Total water soluble phosphorus from streambanks on the Barren Fork Creek from unprotected and failing banks is approximately 1540 kg per year, which represents approximately 10% of the estimated total dissolved phosphorus load.}, journal={2013 Kansas City, Missouri, July 21 - July 24, 2013}, publisher={American Society of Agricultural and Biological Engineers}, author={Fox, Garey A and Miller, Ronald B and Lovern, Sharla and Purvis, Rebecca and Penn, Chad J}, year={2013} }
 @inproceedings{miller_fox_penn_lovern_purvis_2013, title={Sediment and phosphorus loading from protected and unprotected streambanks in Eastern Oklahoma}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84881631367&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2013, ASABE 2013}, author={Miller, R. and Fox, G.A. and Penn, C.J. and Lovern, S. and Purvis, R.}, year={2013}, pages={2584–2594} }
 @article{midgley_fox_wilson_heeren_langendoen_simon_2013, title={Seepage-Induced Streambank Erosion and Instability: In Situ Constant-Head Experiments}, volume={18}, ISSN={1084-0699 1943-5584}, url={http://dx.doi.org/10.1061/(ASCE)HE.1943-5584.0000685}, DOI={10.1061/(ASCE)HE.1943-5584.0000685}, abstractNote={AbstractThe effects of seepage on streambank erosion and failure are less understood compared to fluvial processes, especially the linkage between surface water and groundwater mechanisms. Field data are needed to validate laboratory seepage erosion and instability conclusions and to understand how engineering tools and methods may be applied to field conditions. An innovative trench injection system was utilized to provide a constant head on a near-streambank groundwater system when filled with stream water. This research was performed on a streambank of Dry Creek, a deeply incised stream with near-vertical banks located in Mississippi. Experiments included installing a trench (2.8 m from the bank and 2 m below ground surface) and a network of tensiometers and observation wells to measure soil-water pressures and water table elevations. Bank stratigraphy consisted of a sloping, conductive loamy sand layer between cohesive streambank layers. Groundwater conditions were monitored during a series of induced...}, number={10}, journal={Journal of Hydrologic Engineering}, publisher={American Society of Civil Engineers (ASCE)}, author={Midgley, T. L. and Fox, G. A. and Wilson, G. V. and Heeren, D. M. and Langendoen, E. J. and Simon, A.}, year={2013}, month={Oct}, pages={1200–1210} }
 @article{sheng_fox_abudu_2013, title={Special Section on Interconnection of Atmospheric Water, Surface Water, and Groundwater}, volume={18}, ISSN={1084-0699 1943-5584}, url={http://dx.doi.org/10.1061/(asce)he.1943-5584.0000880}, DOI={10.1061/(asce)he.1943-5584.0000880}, abstractNote={As the climate changes, conjunctive use and management of water resources, or integrated water resources management, has become critically important for water resource planners and managers. Climate variability has resulted in irregular precipitation and temperature patterns, and, in turn, extreme storm events causing floods and frequent droughts. Such extreme events have raised stakeholders’ concerns for water availability. Conjunctive uses of multiple water resources are best management practices/ strategies to address this change in water availability. To implement such strategies, an important aspect gaining a better understanding of the hydrological interconnections among atmospheric water, surface water, and groundwater (three waters) as well as their trends or patterns with climate variations. The Earth’s hydrologic cycle is defined as “the pathway of water as it moves in its various phase through the atmosphere, to the Earth, over and through the land, to the ocean, and back to the atmosphere” (National Research Council 1991). Water in this hydrologic cycle (Chow et al. 1988) may be divided into atmospheric water, surface water, and groundwater (subsurface water). Surface water and atmospheric water transfer to each other through water surface evaporation, evapotranspiration by aquatic plants, and precipitation; groundwater and atmospheric water transfer to each other through near-surface evaporation, evapotranspiration through plants, and deep percolation of precipitation. Surface water and groundwater transfer to each other through seepage when they are hydraulically connected or by infiltration when they are hydraulically disconnected. This three-water transfer has been recognized since the latter part of the seventeenth century (Todd and Mays 2005). The three-water interactions mainly occur on the water’s surface, the land’s surface, and in the vadose zone above the groundwater table, as well as in the hyporheic zone between surface water and groundwater. Along with this water transfer, bio-chemical, physical, and kinetic interactions occur between atmospheric water, surface water, and groundwater. The threewater interactions involve multiple disciplines such as meteorology, surface hydrology, subsurface hydrology, geology, agronomy, pedology, and bio-ecology, to name just a few. Significant advances in understanding three-water interactions have been made over the last several decades. For example, advances in interactions between groundwater and surface water have been overviewed (Winter 1995, 1999; Sophocleous 2002; Diiwu 2003) since the growth in research related to surface-subsurface exchange processes mushroomed during the 1990s (Stanley and Jones 2000). Winter (1995) reviewed advances in understanding the interaction of groundwater and surface water in different landscapes: mountain, riverine, coastal, hummocky, and karst terrains. Winter (1999) proposed three general theoretical considerations regarding the interaction of groundwater with surface water. This interaction is affected by (1) different-scale groundwater flow systems, (2) local soil and geologic controls on seepage distribution, and (3) the magnitude of transpiration directly from groundwater around a surface-water perimeter since this transpiration intercepts potential groundwater inflows or draws water from surface-water bodies. Sophocleous (2002) synthesized and exemplified the interactions between groundwater and surface water in relation to climate, landform, geology, and biotic factors. Diiwu (2003) reviewed fundamental concepts of the ecohydrology of the interaction between groundwater and surface water, and discussed the relevance of this interaction to the sustainable management of water resources in semi-arid regions. A task committee (see subsequent information) was established within the Groundwater Council to promote scientific exchange and share experiences by inviting scientists and researchers to prepare articles and presentations focusing on the state of science relative to the interaction of atmospheric water, surface water, and groundwater, and on the impacts of climate change on water resources, as well as their conjunctive management and uses. This special section includes a collection of invited and peer-reviewed papers including field investigations, numerical simulations, and practical case studies on the following topics: physical/hydrological characterization of interactions; analytical and numerical models for simulating interactions; conjunctive uses and management of the three waters; climate change impacts on interaction of the three waters, including extreme events such as floods and drought; and water quality issues related to such interactions. In this special section, authors present their recent research findings on the interactions of the three waters and their associated processes. It is anticipated that this collection will promote further scientific exchange and further advances of our knowledge in this research area. We are very appreciative of the authors’ contribution and efforts and of the constructive comments and timely reports by reviewers and editors.}, number={10}, journal={Journal of Hydrologic Engineering}, publisher={American Society of Civil Engineers (ASCE)}, author={Sheng, Zhuping and Fox, Garey and Abudu, Shalamu}, year={2013}, month={Oct}, pages={1191–1192} }
 @article{fox_2012, title={A river runs through ASABE}, volume={19}, number={2}, journal={Resource}, author={Fox, G.A.}, year={2012}, pages={SP2} }
 @article{fox_miller_heeren_storm_halihan_2012, title={Authors' Reply}, volume={50}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84863305337&partnerID=MN8TOARS}, DOI={10.1111/j.1745-6584.2012.00939.x}, abstractNote={We appreciate the interest and positive remarks by Reynolds and Lewis in regard to the utility and adoption of the direct-push vadose zone gravel permeameter proposed by Miller et al. (2011). In their comment, Reynolds and Lewis present a summary of recent improvements in solutions for analyzing steady-state conditions in a borehole permeameter, including a solution for zone 1 (water table depth much greater than the test depth) that accounts for soil capillarity. We appreciate their review of these solutions and highlighting ways to expand the utility of the direct-push borehole permeameter across a range of soil types through additional analytical techniques. First, it should be emphasized that the objective of Miller et al. (2011) was to present a direct-push borehole permeameter used to estimate the field-saturated hydraulic conductivity (Kfs) of coarse alluvial gravel soils within the vadose zone of alluvial floodplains. Coarse gravel soils present interesting difficulties regarding excavating boreholes and requiring large volumes of water to maintain a constant head during the test. The directpush steel permeameter and trailer-mounted water tank alleviate these issues. However, the permeameter can be used in other high hydraulic conductivity soils as succinctly pointed out by Reynolds and Lewis. As stated in the conclusions of Miller et al. (2011), “. . .future users may modify the design of the screen to optimize the performance and select alternative analytical methods.” In their comment, Reynolds and Lewis present a solution developed by Reynolds (2010) for the analysis of steady-state flow from a borehole permeameter for soils with capillarity. The Reynolds (2010) solution is another analysis tool that can be used with the direct-push borehole permeameter that does improve the representation of the boundary conditions, expands on applicability in terms of the fact that the steady water depth in the pipe (H) can be much greater than the screen length (L) with no restrictions on the ratio between L and the effective radius of the screen, and is capable of analyzing for soil capillarity in finer grained soils. The question that remains is whether this improved representation and the more complex solution provide meaningful differences in the predicted Kfs for coarse gravels. Therefore, the comment provided an opportunity to investigate differences between predicted Kfs for gravel}, number={4}, journal={Ground Water}, author={Fox, G.A. and Miller, R.B. and Heeren, D.M. and Storm, D.E. and Halihan, T.}, year={2012}, pages={513–513} }
 @article{heeren_fox_storm_2012, title={Berm Method for Quantification of Infiltration and Leaching at the Plot Scale in High Conductivity Soils}, DOI={10.13031/2013.41741}, abstractNote={Measuring infiltration and leaching at the plot scale is difficult, especially for high hydraulic conductivity soils. Infiltration rate has been indirectly calculated at the plot scale by comparing surface runoff to rainfall. Direct measurement of infiltration and leaching beyond the point scale is typically limited to locations where land forming has been performed, e.g. infiltration ponds and fields with basin irrigation. The standard method for field measurement of infiltration is a double ring infiltrometer, which is limited in size (typically 30 cm diameter). In this research, a new method is proposed that uses a temporary berm constructed of a water filled 15 cm diameter vinyl hose with the edges sealed to the soil using bentonite. The berm is capable of confining infiltration plot areas of various sizes (e.g. 1 m by 1 m and 3 m by 3 m areas in this research). Water tanks (0.8 m3 and 4.9 m3) and gravity flow were used to supply water and tracers to the plots. A constant head was maintained within the plot automatically using float valves for lower flow rates and manually with a gate valve for higher flow rates. Observation wells were installed 0.5 m outside the plot to monitor for water table rise and tracers that leached into the groundwater. The procedure was tested on soils ranging from silt loam to coarse gravel with measured infiltration rates ranging from 5 to 70 cm/hr. Guidelines are provided for tank size and refilling frequency for field experiments. In addition, numerical simulations were performed to estimate time of response in wells for various soil and experimental design conditions.}, journal={2012 Dallas, Texas, July 29 - August 1, 2012}, publisher={American Society of Agricultural and Biological Engineers}, author={Heeren, Derek M and Fox, Garey A and Storm, Daniel E}, year={2012} }
 @inproceedings{heeren_fox_storm_2012, title={Berm method for quantification of infiltration and leaching at the plot scale in high conductivity soils}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84871740999&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2012, ASABE 2012}, author={Heeren, D.M. and Fox, G.A. and Storm, D.E.}, year={2012}, pages={668–677} }
 @article{purvis_fox_2012, title={Controlled Laboratory Experiments Investigating the Influence of Shallow Groundwater Tables on Runoff through Vegetative Filter Strips}, DOI={10.13031/2013.41758}, abstractNote={Vegetative filter strips (VFS) are implemented adjacent to surface water bodies with the purpose of slowing down runoff and allowing for infiltration and settling of particles. However, there is currently limited data demonstrating how VFS perform under shallow water table conditions. Future versions of VFS design models are being constructed for this case and therefore a need exists to derive data to validate the model. The objectives of this research were to simulate a VFS in a controlled laboratory setting to quantify the influence of shallow groundwater tables on runoff. A steel box (100 cm wide, 200 cm long and 70 cm deep) was used to simulate surface runoff through a VFS. A silt loam soil was packed in the box and planted with Bermuda grass. Five experiments were performed by controlling the groundwater table including a free drainage case, a series of static water table cases, and a dynamic water table case. Precipitation was not considered in these experiments. Water was evenly distributed onto the upslope end of the VFS at a steady rate and outflow measured at the downslope end. The influence of the water table position on the outflow rate and infiltration was determined. As expected, results indicated that the higher the groundwater table the less infiltration occurred. A water table near the ground surface (1 to 2 cm) for this silt loam soil was required to limit infiltration such that the inflow and outflow rates were approximately equivalent. The dynamic water table case demonstrated that the water table can rapidly increase near the soil surface due to infiltration in the VFS. In cases with shallow groundwater, less infiltration will result in less removal of contaminants in the runoff and therefore greater quantities of contaminants reaching nearby surface water bodies. The experimental data will be critical for validating future VFS design models that will consider the performance of VFS in areas of shallow groundwater.}, journal={2012 Dallas, Texas, July 29 - August 1, 2012}, publisher={American Society of Agricultural and Biological Engineers}, author={Purvis, Rebecca and Fox, Garey A}, year={2012} }
 @inproceedings{purvis_fox_2012, title={Controlled laboratory experiments investigating the influence of shallow groundwater tables on runoff through vegetative filter strips}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84871807759&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2012, ASABE 2012}, author={Purvis, R. and Fox, G.A.}, year={2012}, pages={976–986} }
 @inproceedings{al-madhhachi_fox_hanson_tyagi_bulut_2012, title={Development a fluvial detachment rate model to predict the erodibility of cohesive soils under the influence of seepage}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84871816499&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2012, ASABE 2012}, author={Al-Madhhachi, A.-S.T. and Fox, G.A. and Hanson, G.J. and Tyagi, A.K. and Bulut, R.}, year={2012}, pages={946–975} }
 @article{fox_marvin_guzman_hoang_malone_kanwar_shipitalo_2012, title={E. coli transport through surface-connected biopores identified from smoke injection tests}, volume={55}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84872566252&partnerID=MN8TOARS}, number={6}, journal={Transactions of the ASABE}, author={Fox, G.A. and Marvin, M.M. and Guzman, J.A. and Hoang, C.K. and Malone, R.W. and Kanwar, R.S. and Shipitalo, M.J.}, year={2012}, pages={2185–2194} }
 @inproceedings{penn_fox_2012, title={Enhancing engagement in assessment through a systematic faculty development program}, author={Penn, J. and Fox, G.A.}, year={2012} }
 @article{midgley_fox_heeren_2012, title={Evaluation of the bank stability and toe erosion model (BSTEM) for predicting lateral retreat on composite streambanks}, volume={145-146}, url={http://dx.doi.org/10.1016/j.geomorph.2011.12.044}, DOI={10.1016/j.geomorph.2011.12.044}, abstractNote={Streambank erosion is known to be a major source of sediment in streams and rivers. The Bank Stability and Toe Erosion Model (BSTEM) was developed in order to predict streambank retreat due to both fluvial erosion and geotechnical failure. However, few, if any, model evaluations using long-term streambank retreat data have been performed. The objectives of this research were to (1) monitor long-term composite streambank retreat during a hydraulically active period on a rapidly migrating stream, (2) evaluate BSTEM's ability to predict the measured streambank retreat, and (3) assess the importance of accurate geotechnical, fluvial erosion, and near-bank pore-water pressure properties. The Barren Fork Creek in northeastern Oklahoma laterally eroded 7.8 to 20.9 m along a 100-m length of stream between April and October 2009 based on regular bank location surveys. The most significant lateral retreat occurred in mid- to late-May and September due to a series of storm events, and not necessarily the most extreme events observed during the monitoring period. BSTEM (version 5.2) was not originally programmed to run multiple hydrographs iteratively, so a subroutine was written that automatically input the temporal sequence of stream stage and to lag the water table in the near-bank ground water depending on user settings. Eight BSTEM simulations of the Barren Fork Creek streambank were performed using combinations of the following input data: with and without a water table lag; default BSTEM geotechnical parameters (moderate silt loam) versus laboratory measured geotechnical parameters based on direct shear tests on saturated soil samples; and default BSTEM fluvial erosion parameters versus field measured fluvial erosion parameters from submerged jet tests. Using default BSTEM input values underestimated the actual erosion that occurred. Lagging the water table predicted more geotechnical failures resulting in greater streambank retreat. Using measured fluvial and geotechnical parameters and a water table lag also under predicted retreat (approximately 3.3 m), but did predict the appropriate timing of streambank collapses. The under prediction of retreat was hypothesized to be due to over predicting the critical shear stress of the non-cohesive gravel, under predicting the erodibility of the non-cohesive gravel, and/or under predicting the imposed shear stress acting on the streambank. Current research improving our understanding of shear stress distributions, streambank pore-water pressure dynamics, and methods for estimating excess shear stress parameters for noncohesive soils will be critical for improving BSTEM and other streambank stability models.}, journal={Geomorphology}, author={Midgley, T.L. and Fox, G.A. and Heeren, D.M.}, year={2012}, month={Apr}, pages={107–114} }
 @inproceedings{akay_özer_fox_2012, place={Madrid}, title={Experimental investigation of failure mechanisms of expanded polystryrene block geofoam slope system under seepage}, ISBN={9788469546888}, booktitle={EuroGeo 5 : proceedings of the fifth Geosynthetics Congress, Valencia, Spain, 16-19 September 2012}, publisher={R.B. Servicios Editoriales}, author={Akay, O. and Özer, A.T. and Fox, G.A.}, year={2012} }
 @article{guzman_fox_2012, title={Implementation of biopore and soil fecal bacteria fate and transport routines in the root zone water quality model (RZWQM)}, volume={55}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84859784669&partnerID=MN8TOARS}, number={1}, journal={Transactions of the ASABE}, author={Guzman, J.A. and Fox, G.A.}, year={2012}, pages={73–84} }
 @article{heeren_fox_storm_storm_haggard_halihan_miller_2012, title={Quantification and Heterogeneity of Infiltration and Transport in Alluvial Floodplains}, DOI={10.13031/2013.41740}, abstractNote={In order to protect drinking water systems and aquatic ecosystems, all critical nutrient source areas and transport mechanisms need to be characterized. It is hypothesized that hydrologic heterogeneities (e.g., macropores and gravel outcrops) in the subsurface of floodplains play an integral role in impacting flow and contaminant transport between the soil surface and shallow alluvial aquifers which are intricately connected to streams. Infiltration is often assumed to be uniform at the field scale, but this neglects the high spatial variability common in anisotropic, heterogeneous alluvial floodplain soils. In the Ozark ecoregion, for example, the erosion of carbonate bedrock (primarily limestone) by slightly acidic water has left a large residuum of chert gravel in Ozark soils, with floodplains generally consisting of coarse chert gravel overlain by a mantle (1 to 300 cm) of gravelly loam or silt loam. The process of alluvial sediment deposition is highly variable, and can cause gravel layers to outcrop on the soil surface at various locations within a floodplain. The objective of this research was to quantify heterogeneity in infiltration rates at three floodplain sites in the Ozark ecoregion of Oklahoma and Arkansas. Innovative field studies, including plot scale (1 by 1 m and 3 by 3 m) solute injection experiments along with geophysical imaging, were performed on both gravel outcrops and non-gravel outcrops. Plots maintained a constant head of 3 to 10 cm for up to 48 hours. Infiltration rates varied from 0.8 to 70 cm/h, and varied considerably even within a single floodplain. Electrical resistivity imaging was used to identify zones of preferential flow as well as characterize subsurface soil layering. Fluid samples from observation wells outside the plot (0.5 m from the boundary) indicated nonuniform subsurface flow and transport. Phosphorus was detected in the groundwater for 6 of the 12 plots and was positively correlated to the presence of gravel outcrops. Results indicated that flow paths are sub-meter scale for detecting infiltrating solutions. Tension infiltrometers showed that macropore flow accounted for approximately 85% to 99% of the total infiltration.}, journal={2012 Dallas, Texas, July 29 - August 1, 2012}, publisher={American Society of Agricultural and Biological Engineers}, author={Heeren, Derek M and Fox, Garey A and Storm, Daniel E and Storm, Peter Q and Haggard, Brian E and Halihan, Todd and Miller, Ronald B}, year={2012} }
 @inproceedings{heeren_fox_storm_storm_haggard_halihan_miller_2012, title={Quantification and heterogeneity of infiltration and transport in alluvial floodplains}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84871725648&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2012, ASABE 2012}, author={Heeren, D.M. and Fox, G.A. and Storm, D.E. and Storm, P.Q. and Haggard, B.E. and Halihan, T. and Miller, R.B.}, year={2012}, pages={647–667} }
 @article{meek_hoang_malone_kanwar_fox_guzman_shipitalo_2012, title={Rational polynomial functions for modeling E. coli and bromide breakthrough}, volume={55}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84872293127&partnerID=MN8TOARS}, number={5}, journal={Transactions of the ASABE}, author={Meek, D.W. and Hoang, C.K. and Malone, R.W. and Kanwar, R.S. and Fox, G.A. and Guzman, J.A. and Shipitalo, M.J.}, year={2012}, pages={1821–1826} }
 @article{fox_wilson_2012, title={Seepage and piping: Solitary and integrated mechanisms of streambank erosion and failure}, volume={19}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84861981195&partnerID=MN8TOARS}, number={2}, journal={Resource: Engineering and Technology for Sustainable World}, author={Fox, G. and Wilson, G.V.}, year={2012} }
 @article{guzman_fox_penn_2012, title={Sorption of Escherichia Coli in agricultural soils influenced by swine manure constituents}, volume={55}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84859750458&partnerID=MN8TOARS}, number={1}, journal={Transactions of the ASABE}, author={Guzman, J.A. and Fox, G.A. and Penn, C.J.}, year={2012}, pages={61–71} }
 @article{midgley_fox_felice_wilson_2012, title={Streambank Piping and Internal Erosion as Failure Mechanisms of Streambanks}, DOI={10.13031/2013.41757}, abstractNote={Soil piping has been attributed as a potential mechanism of instability of embankments and streambanks. Limited field work has been conducted on quantifying and modeling pipeflow and internal erosion processes in the field with either natural or artificially created soil pipes. This research utilized an innovative constant-head trench system to conduct constant head soil pipe experiments in two contrasting streambanks: Dry Creek in northern Mississippi and Cow Creek in northern Oklahoma. Experiments included “open pipes” where the soil pipe was directly connected to the constant-head trench and open at the streambank face and “clogged pipes” which involved plugging the outlet of the soil pipe using soil excavated adjacent to the pipe. A tensiometer network was used to measure soil water pressures surrounding “open” and “clogged” pipe outlets on the streambank face. When pipeflow occurred, flow and sediment samples were collected using flow collection pans to quantify sediment concentrations and pipe enlargement. Flow and sediment data were used with an existing turbulent pipeflow and internal erosion model to estimate erodibility and critical shear stress properties of the soils, which were subsequently compared to similar properties derived from jet erosion tests. “Clogged” soil pipes resulted in pore water pressure increases in the soil adjacent to the pipe, which generally remained below saturation during these experimental periods, except locations close to the plug. Depending on the density of the plugged soil material, the “clogged” soil pipes either burst resulting in turbulent pipeflow or were manually punctured to establish pipeflow. Calibrated critical shear stress from the turbulent pipeflow and internal erosion model matched that observed from jet erosion tests for the less erodible soils on the Dry Creek streambank where sediment concentrations were consistently below 2 g L-1 even with fairly large hydraulic gradients on the pipe (0.3 m m-1). Calibrated erodibility coefficients were much smaller than those measured with jet erosion tests. For the more erodible streambank soils of Cow Creek, sediment concentrations approached 40 g L-1. There is a need for improved pipeflow modeling that accounts for partially filled soil pipes and pipeflow/soil matrix interactions leading to cases of steady flow rates but increasing sediment concentrations during the initial stages of pipeflow.}, journal={2012 Dallas, Texas, July 29 - August 1, 2012}, publisher={American Society of Agricultural and Biological Engineers}, author={Midgley, Taber L and Fox, Garey A and Felice, Rachel M and Wilson, Glenn V}, year={2012} }
 @inproceedings{midgley_fox_wilson_felice_2012, title={Streambank piping and internal erosion as failure mechanisms of streambanks}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84871750753&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2012, ASABE 2012}, author={Midgley, T.L. and Fox, G.A. and Wilson, G.V. and Felice, R.M.}, year={2012}, pages={931–945} }
 @article{lovern_fox_2012, title={Streambank research facility at Oklahoma State university}, volume={19}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84861991539&partnerID=MN8TOARS}, number={2}, journal={Resource: Engineering and Technology for Sustainable World}, author={Lovern, S.B. and Fox, G.}, year={2012} }
 @article{penn_mcgrath_rounds_fox_heeren_2012, title={Trapping phosphorus in runoff with a phosphorus removal structure}, volume={41}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84862244589&partnerID=MN8TOARS}, DOI={10.2134/jeq2011.0045}, abstractNote={Reduction of phosphorus (P) inputs to surface waters may decrease eutrophication. Some researchers have proposed filtering dissolved P in runoff with P-sorptive byproducts in structures placed in hydrologically active areas with high soil P concentrations. The objectives of this study were to construct and monitor a P removal structure in a suburban watershed and test the ability of empirically developed flow-through equations to predict structure performance. Steel slag was used as the P sorption material in the P removal structure. Water samples were collected before and after the structure using automatic samples and analyzed for total dissolved P. During the first 5 mo of structure operation, 25% of all dissolved P was removed from rainfall and irrigation events. Phosphorus was removed more efficiently during low flow rate irrigation events with a high retention time than during high flow rate rainfall events with a low retention time. The six largest flow events occurred during storm flow and accounted for 75% of the P entering the structure and 54% of the P removed by the structure. Flow-through equations developed for predicting structure performance produced reasonable estimates of structure "lifetime" (16.8 mo). However, the equations overpredicted cumulative P removal. This was likely due to differences in pH, total Ca and Fe, and alkalinity between the slag used in the structure and the slag used for model development. This suggests the need for an overall model that can predict structure performance based on individual material properties.}, number={3}, journal={Journal of Environmental Quality}, author={Penn, C.J. and McGrath, J.M. and Rounds, E. and Fox, G. and Heeren, D.}, year={2012}, pages={672–679} }
 @article{heeren_mittelstet_fox_storm_al-madhhachi_midgley_stringer_stunkel_tejral_2012, title={Using rapid geomorphic assessments to assess streambank stability in oklahoma ozark streams}, volume={55}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84863663950&partnerID=MN8TOARS}, number={3}, journal={Transactions of the ASABE}, author={Heeren, D.M. and Mittelstet, A.R. and Fox, G.A. and Storm, D.E. and Al-Madhhachi, A.T. and Midgley, T.L. and Stringer, A.F. and Stunkel, K.B. and Tejral, R.D.}, year={2012}, pages={957–968} }
 @inproceedings{heeren_mittelstet_fox_storm_2011, title={Assessing streambank stability of oklahoma ozark streams with rapid geomorphic assessments}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79960395760&partnerID=MN8TOARS}, DOI={10.1061/41173(414)408}, abstractNote={Streams in the Ozark Ecoregion naturally meander and have a high degree of sinuosity. Changes in land use have resulted in accelerated rates of streambank erosion. Numerous benefits may be achieved from streambank stabilization, but more information is needed on the most critical locations for investing limited funds. Rapid geomorphic assessments (RGAs) are indices proposed to aid in prioritizing sites. This research (1) evaluated two RGAs, the Bank Erosion Hazard Index (BEHI) and the Channel Stability Index (CSI), on several stream sites along the Barren Fork Creek and Spavinaw Creek, and (2) developed a new RGA specific to the ecoregion. The performance of the RGAs was assessed based on lateral bank erosion estimated from five years of aerial photography. Correlations between the existing RGAs and lateral bank erosion were relatively low with coefficients of determination, R2, of 0.23 and 0.19 for CSI and BEHI, respectively. The two RGAs failed to indicate the same reaches as the most unstable. Primary limitations were not considering the streambank's cohesion and the difficulty in accurately assessing some metrics. Therefore, the Ozark Stream Erosion Potential Index (OSEPI) was developed by including parameters to account for bank cohesion and stream curvature. The OSEPI had the highest correlation (R2 of 0.31 for all sites; R2 of 0.46 for sites with similar soils) to measured streambank erosion and aided in prioritizing sites.}, booktitle={World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability - Proceedings of the 2011 World Environmental and Water Resources Congress}, author={Heeren, D.M. and Mittelstet, A.R. and Fox, G.A. and Storm, D.E.}, year={2011}, pages={3907–3916} }
 @article{mittelstet_smolen_fox_adams_2011, title={Comparison of Aquifer Sustainability Under Groundwater Administrations in Oklahoma and Texas1}, volume={47}, ISSN={1093-474X}, url={http://dx.doi.org/10.1111/j.1752-1688.2011.00524.x}, DOI={10.1111/j.1752-1688.2011.00524.x}, abstractNote={Mittelstet, Aaron R., Michael D. Smolen, Garey A. Fox, and Damian C. Adams, 2011. Comparison of Aquifer Sustainability Under Groundwater Administrations in Oklahoma and Texas. Journal of the American Water Resources Association (JAWRA) 1‐8. DOI: 10.1111/j.1752‐1688.2011.00524.x}, number={2}, journal={JAWRA Journal of the American Water Resources Association}, publisher={Wiley}, author={Mittelstet, Aaron R. and Smolen, Michael D. and Fox, Garey A. and Adams, Damian C.}, year={2011}, month={Mar}, pages={424–431} }
 @article{mittelstet_heeren_fox_storm_white_miller_2011, title={Comparison of subsurface and surface runoff phosphorus transport rates in alluvial floodplains}, volume={141}, ISSN={0167-8809}, url={http://dx.doi.org/10.1016/j.agee.2011.04.006}, DOI={10.1016/j.agee.2011.04.006}, abstractNote={Phosphorus (P) loading to streams can occur by both surface runoff and subsurface transport, with subsurface P transport often assumed negligible. Groundwater P concentrations in alluvial aquifers can be significant, especially in preferential flow paths (PFPs). The objectives of this research were to quantify subsurface P transport rates at two sites in northeastern Oklahoma and to compare them with surface runoff P transport rates derived from a hydrologic model, the Pasture Phosphorus Management Calculator (PPM Plus). Ozark ecoregion study sites were adjacent to the Barren Fork Creek and Honey Creek in northeastern OK, USA. Each site, instrumented with 24 observation wells, was monitored for several months for both groundwater levels and P concentrations. Using the flow and P concentration data, Monte Carlo simulations with Darcy's Law and a P transport rate equation were used to calculate the distributions of subsurface P transport rates across a transect within the well field containing a single identified PFP. Total subsurface P transport rates, through both the non-PFP flow domain and a single PFP, were estimated to be 0.04 kg year−1 and 0.03 kg year−1 for the Barren Fork Creek and Honey Creek field sites, respectively. Monte Carlo simulations for surface runoff P transport rates with PPM Plus resulted in average total P surface runoff transport rates of 0.07 kg year−1 for the Barren Fork Creek site and 0.08 kg year−1 for the Honey Creek site. For the groundwater at these floodplains, the P source was P-laden stream water flowing into the alluvial aquifer and a minimal quantity of P leaching from the surface. Results indicated that the subsurface P transport rates for small (3 ha) alluvial floodplain sites in the Ozark ecoregion were at least 0.03–0.04 kg year−1, although subsurface P transport rates may be higher in cases with greater numbers of PFPs and where the subsurface is connected to a larger P source.}, number={3-4}, journal={Agriculture, Ecosystems & Environment}, publisher={Elsevier BV}, author={Mittelstet, Aaron R. and Heeren, Derek M. and Fox, Garey A. and Storm, Daniel E. and White, Michael J. and Miller, Ronald B.}, year={2011}, month={May}, pages={417–425} }
 @article{miller_heeren_fox_storm_halihan_2011, title={Design and Application of a Direct-Push Vadose Zone Gravel Permeameter}, volume={49}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-80052945273&partnerID=MN8TOARS}, DOI={10.1111/j.1745-6584.2010.00796.x}, abstractNote={A borehole permeameter is well suited for testing saturated hydraulic conductivity (Ksat) at specific depths in the vadose zone. Most applications of the method involve fine‐grained soils that allow hand auguring of test holes and require a small water reservoir to maintain a constant head. In non‐cohesive gravels, hand‐dug test holes are difficult to excavate, holes are prone to collapse, and large volumes of water are necessary to maintain a constant head for the duration of the test. For coarse alluvial gravels, a direct‐push steel permeameter was designed to place a slotted pipe at a specific sampling depth. Measurements can be made at successive depths at the same location. A 3790 L (1000 gallons) trailer‐mounted water tank maintained a constant head in the permeameter. Head in the portable tank was measured with a pressure transducer and flow was calculated based on a volumetric rating curve. A U.S. Bureau of Reclamation analytical method was utilized to calculate Ksat. Measurements with the permeameter at a field site were similar to those reported from falling‐head tests.}, number={6}, journal={Ground Water}, author={Miller, R.B. and Heeren, D.M. and Fox, G.A. and Storm, D.E. and Halihan, T.}, year={2011}, pages={920–925} }
 @article{fox_matlock_guzman_sahoo_stunkel_2011, title={Escherichia coli
 Load Reduction from Runoff by Vegetative Filter Strips: A Laboratory-Scale Study}, volume={40}, ISSN={0047-2425}, url={http://dx.doi.org/10.2134/jeq2010.0391}, DOI={10.2134/jeq2010.0391}, abstractNote={Vegetative filter strips (VFS) are commonly used best management practices for removing contaminants from runoff. Additional research is warranted to determine their efficiency and the most appropriate metrics for predicting fecal bacteria reductions. The objective of this research was to determine VFS effectiveness in removing from runoff relative to inflow rate, infiltration capacity, and flow concentration. This research also investigated the presence of in runoff from clean water runon after diluted manure runon events. A laboratory-scale VFS soil box (200 cm long, 100 cm wide, 7.5% slope) was packed with a sandy loam soil. Ten constant-flow VFS experiments were conducted with and without vegetation (8-10 cm ryegrass [ L.]) at low (20-40 cm s), medium (40-60 cm s), and high (85-120 cm s) flow rates and for a full (100 cm) or concentrated (40 cm) VFS flow width to simulate a channelizing flow condition. Two runon events were investigated for each experimental condition: (i) diluted liquid swine manure runon and (ii) clean water runon 48 h afterward. was used as an indicator of fecal contamination and was quantified by the most probable number (MPN) technique. No concentration reductions were observed based on peak outflow concentrations, and only small concentration reductions were observed based on outflow event mean concentrations. The mass reductions ranged from 22 to 71% and were strongly correlated to infiltration or runoff reduction ( = 0.88), which was dependent on the degree of flow concentration. Little to no effect of sedimentation on transport was observed, hypothesized to be due to minimum attachment to sediment particles because the bacteria originated from manure sources. Therefore, the design of VFS for bacteria removal should be based on the infiltration capacity in the VFS and should prevent concentrated flow, which limits total infiltration. The event mean concentrations in clean water runon experiments were between 10 and 100 MPN per 100 mL; therefore, under these conditions, VFS served as a source of residual from previous runon events.}, number={3}, journal={Journal of Environmental Quality}, publisher={Wiley}, author={Fox, Garey A. and Matlock, Emily M. and Guzman, Jorge A. and Sahoo, Debabrata and Stunkel, Kevin B.}, year={2011}, month={May}, pages={980–988} }
 @article{fox_heeren_kizer_2011, title={Evaluation of a stream-aquifer analysis test for deriving reach-scale streambed conductance}, volume={54}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79954527847&partnerID=MN8TOARS}, number={2}, journal={Transactions of the ASABE}, author={Fox, G.A. and Heeren, D.M. and Kizer, M.A.}, year={2011}, pages={473–479} }
 @inproceedings{midgley_fox_heeren_2011, title={Evaluation of the Bank Stability and Toe Erosion Model (BSTEM) for predicting lateral streambank retreat on ozark streams}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79960424136&partnerID=MN8TOARS}, DOI={10.1061/41173(414)209}, abstractNote={Streambank erosion is known to be a major source of sediment in streams and rivers. The Bank Stability and Toe Erosion Model (BSTEM) was developed by the USDA-ARS National Sedimentation Laboratory in order to predict streambank retreat due to both fluvial erosion and geotechnical failure. Few model evaluations for bank retreat have been performed to date. The objective of this research was to evaluate BSTEM's ability to predict bank retreat on Ozark ecoregion streams, assess the importance of accurate geotechnical and fluvial erosion soil parameter values, and evaluate the importance of the near bank water table elevation on bank stability. The model was applied to a streambank on the Barren Fork Creek in northeastern Oklahoma. This site experienced significant bank retreat (between 7.8 and 20.9 m over a 100-m length of stream) between April and October 2009 based on regular surveys of the bank profile. BSTEM (version 5.2) was not originally programmed to run multiple hydrographs iteratively, so an additional subroutine was written which automatically input the stream stage. The new subroutine was also written to lag the water table response in the near-bank ground water depending on user settings. Eight BSTEM simulations were performed using combinations of the following input data: with and without a water table lag; default BSTEM geotechnical parameters (moderate silt loam) versus laboratory measured geotechnical parameters for the silt loam layer based on direct shear tests on saturated soil samples; and default BSTEM fluvial erosion parameters versus field measured fluvial erosion parameters from submerged jet tests on the silt loam layer. Using default BSTEM input values underestimated the actual erosion that occurred. Lagging the water table predicted more geotechnical failures resulting in greater bank retreat. Using measured fluvial and geotechnical parameters and a water table lag also under predicted bank retreat (approximately 4.0 m), but did predict the appropriate timing of bank collapses.}, booktitle={World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability - Proceedings of the 2011 World Environmental and Water Resources Congress}, author={Midgley, T.L. and Fox, G.A. and Heeren, D.M.}, year={2011}, pages={1991–2000} }
 @article{fox_heeren_miller_mittelstet_storm_2011, title={Flow and transport experiments for a streambank seep originating from a preferential flow pathway}, volume={403}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79956341660&partnerID=MN8TOARS}, DOI={10.1016/j.jhydrol.2011.04.014}, abstractNote={Streambank seeps commonly originate from localized heterogeneity or preferential flow pathways (PFPs) in riparian floodplains. However, limited field data have been reported on ground water seep flows and solute transport to seeps from PFPs. The objective of this research was to build upon previous floodplain-scale investigations of PFPs by analyzing seep discharge and transport characteristics through a single PFP. An important research question was whether this PFP could be conceptualized as a homogeneous, one-dimensional flow path. Streambank seep discharge measurements were obtained by inducing a hydraulic head in a trench injection system. Also, co-injection of Rhodamine WT (RhWT) and a potassium chloride (KCl) tracer over a 60-min period was used to investigate transport dynamics. Seep discharge and breakthrough curves for electrical conductivity (EC) and RhWT were measured at the streambank using a lateral flow collection device. The breakthrough curves were fit to one-dimensional convective-dispersion equations (CDEs) to inversely estimate solute transport parameters. The PFP from which the seep originated was clean, coarse gravel (6% by mass less than 2.0 mm) surrounded by gravel with finer particles (20% by mass less than 2.0 mm). Located approximately 2 m from the trench, the seep (50 cm by 10 cm area) required at least 40 cm of hydraulic head for flow to emerge at the streambank. At a higher hydraulic head of 125 cm, seep discharge peaked at 3.5 L/min. This research verified that localized PFPs can result in the rapid transport of water (hydraulic conductivity on the order of 400 m/d) and solutes once reaching a sufficient near-bank hydraulic head. A one-dimensional equilibrium CDE was capable of simulating the EC (R2 = 0.94) and RhWT (R2 = 0.91) breakthrough curves with minimal RhWT sorption (distribution coefficient, Kd, equal to 0.1 cm3/g). Therefore, the PFP could be conceptualized as a one-dimensional, homogenous flow and transport pathway. These results are consistent with previous research observing larger-scale phosphorus transport.}, number={3-4}, journal={Journal of Hydrology}, author={Fox, G.A. and Heeren, D.M. and Miller, R.B. and Mittelstet, A.R. and Storm, D.E.}, year={2011}, pages={360–366} }
 @article{fox_wilson_midgley_almadhhachi_carson_2011, title={Groundwater Seepage Mechanisms of Streambank Erosion and Failure}, DOI={10.13031/2013.39206}, abstractNote={The importance of groundwater seepage and pipeflow is unknown with respect to other fundamental processes of streambank erosion and failure, although seepage and pipeflow features are observed on streambanks throughout the world that span a range of geomorphologic conditions. Previous field and laboratory research on seepage erosion has demonstrated that groundwater seepage and pipeflow play an important role in the erosion and failure of streambanks. This previous research pointed to seepage forces and undercutting as causes, independent of fluvial forces, of bank failures in some stream systems. Specific seepage and pipeflow mechanisms that cause bank failure may never manifest themselves as transparent features on unstable banks. The objective of this research was to conduct more in-depth laboratory and field experiments to determine how groundwater flow mechanisms, potentially in combination with fluvial processes, affect the occurrence and timing of streambank erosion and failure. Current research activities include conducting three-dimensional soil column experiments to determine the occurrence and prevalence of different seepage erosion mechanisms (i.e., seepage gradient forces and undercutting) across a range of soil textures and cohesions and to identify typical undercut formations when seepage undercutting occurs. Seepage undercuts only formed in sands with a bulk density greater than 1.35 g/cm3 and in loamy sands with a bulk density greater than 1.50 g/cm3. For soils with greater clay content, seepage erosion undercuts may not occur under typical bulk densities. This research also monitored pore-water pressures in a streambank on Dry Creek, a tributary to Little Topashaw Creek located in Chickasaw County, Mississippi, before and during an induced seepage experiment. Seepage flow and erosion rates were measured in four separate experiments on three seeps and demonstrated the capability of seepage to rapidly destabilize streambanks, especially when acting in concert with processes that remove deposited material from the seepage undercut. Usually the erosion rate of cohesive soils from fluvial forces is computed using an excess shear stress equation, dependent on two major soil parameters: the critical shear stress and the erodibility coefficient. A submerged jet test apparatus is one method for measuring these parameters. In this study, a new miniature version of the jet test device and a seepage column were utilized to measure the erodibility of cohesive soils influenced by seepage. Erodibility of cohesive soils exponentially increased with higher seepage gradients. These laboratory and field experiments have further demonstrated the importance of considering seepage mechanisms relative to bank and hillslope stability. Groundwater forces can act over extended periods to destabilize banks between flow events, but specific seepage mechanisms become prevalent under certain streambank stratigraphy and hydrologic conditions.}, journal={International Symposium on Erosion and Landscape Evolution (ISELE), 18-21 September 2011, Anchorage, Alaska}, publisher={American Society of Agricultural and Biological Engineers}, author={Fox, Garey A and Wilson, Glenn V and Midgley, Taber and Almadhhachi, Abdulsahib and Carson, Rachel}, year={2011} }
 @inproceedings{fox_wilson_midgley_almadhhachi_carson_2011, title={Groundwater seepage mechanisms of streambank erosion and failure}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84861644621&partnerID=MN8TOARS}, booktitle={ASABE - International Symposium on Erosion and Landscape Evolution 2011}, author={Fox, G.A. and Wilson, G.V. and Midgley, T. and Almadhhachi, A. and Carson, R.}, year={2011}, pages={25–33} }
 @inproceedings{al-madhhachi_hanson_fox_tyagi_bulut_2011, title={Measuring erodibility of cohesive soils using laboratory jet erosion tests}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79960437161&partnerID=MN8TOARS}, DOI={10.1061/41173(414)244}, abstractNote={Many factors affect the erodibility of cohesive soils, such as the soil characteristics, soil moisture content, and properties of the eroding fluid. Typically the erosion rate of cohesive soils is quantified using an excess shear stress equation, dependent on two major soil parameters: the critical shear stress (τc) and the erodibility coefficient (kd). A submerged jet test (JET — Jet Erosion Test) is one method for measuring these parameters. In this study, a laboratory JET and a new miniature version of the device ("mini" JET), with the advantage of being easier to use in the field, were used to measure τc and kd for various soils. The objective of this study was to determine if the "mini" JET estimated equivalent values for τc and kd. Two different soils types (silty sand and clayey sand) were used in comparing the performance of the two devices. Sieve analysis, hydrometer, and plasticity index tests were also performed to characterize these two soils. Test samples of the soils were prepared at three to seven different water contents with equivalent compaction effort (25 blows per layer). In-order to compare the performance and repeatability of both JET devices, tests were performed on paired samples prepared in the same way and tested at the same time. Reasonably equivalent measured kd were obtained with the two JET devices for both soils. Results indicated some variability in measuring τc and kd due to variability in the subsamples of the cohesive soil and differences in soil moisture levels. These results also indicated that settling back of some of the eroded soil into the scour area of the new "mini" JET device may have caused differences in measured τc relative to the original JET device. Even though there was an observed difference in the observed τc, the differences were consistent. The relationships between measured τc and kd obtained from both JET devices also compared reasonably well with those observed in previous field research.}, booktitle={World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability - Proceedings of the 2011 World Environmental and Water Resources Congress}, author={Al-Madhhachi, A.T. and Hanson, G.J. and Fox, G.A. and Tyagi, A.K. and Bulut, R.}, year={2011}, pages={2350–2359} }
 @inproceedings{al-madhhachi_fox_tyagi_hanson_bulut_2011, title={Measuring the erodibility of cohesive soils influenced by seepage forces using a laboratory jet erosion test device}, volume={4}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-81255171946&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2011, ASABE 2011}, author={Al-Madhhachi, A.-S.T. and Fox, G.A. and Tyagi, A.K. and Hanson, G.J. and Bulut, R.}, year={2011}, pages={3030–3041} }
 @article{fox_elliott_bellmer_2011, title={Option-specific student outcomes to meet biological engineering program criteria}, volume={27}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-80053937677&partnerID=MN8TOARS}, number={5}, journal={Applied Engineering in Agriculture}, author={Fox, G.A. and Elliott, R.L. and Bellmer, D.}, year={2011}, pages={857–860} }
 @article{heeren_fox_miller_storm_fox_penn_halihan_mittelstet_2011, title={Stage-dependent transient storage of phosphorus in alluvial floodplains}, volume={25}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-80052952199&partnerID=MN8TOARS}, DOI={10.1002/hyp.8054}, abstractNote={Abstract}, number={20}, journal={Hydrological Processes}, author={Heeren, D.M. and Fox, G.A. and Miller, R.B. and Storm, D.E. and Fox, A.K. and Penn, C.J. and Halihan, T. and Mittelstet, A.R.}, year={2011}, pages={3230–3243} }
 @article{midgley_fox_wilson_heeren_simon_langendoen_2011, title={Streambank Erosion and Instability Induced by Groundwater Seepage}, DOI={10.13031/2013.37385}, abstractNote={Excessive sediment is one of the most common surface water pollutants. It diminishes water quality and destroys aquatic habitat. Streambank erosion is known to be a major source of sediment in streams and rivers, contributing as much as 80% of the total sediment load in some watersheds. Little work has been done to study the effects of seepage on streambank erosion and failure. Prior research, primarily in the laboratory under well-defined and controlled conditions, has examined seepage as a mechanism for bank erosion, but more needs to be done to validate conclusions derived from the laboratory with field data. This project studied a streambank on Dry Creek (a tributary to Little Topashaw Creek) located in Chickasaw County, Mississippi. The bank was previously observed to produce seepage even during dry summer months. This creek is a deeply incised stream in the Yalobusha Watershed with near 90 degree banks. The creek flows through alluvial plains under cultivation and surrounded by forested areas. Excess sediment has been identified as the main water quality issue in the watershed with gullies and banks being the main sources. Watershed geology is characterized by silt loam and clay loam with a more conductive loamy sand between the loam and an underlying cohesive layer. The site was initially instrumented with a network of tensiometers and observation wells. Groundwater conditions and bank erosion were monitored for several weeks, followed by an induced seepage experiment. A trench installed 2.8 m from the edge of the bank and approximately 2 m below ground surface was used to provide a constant head for groundwater flow in the near-bank area. The bank face was outfitted with a seepage collection device that measured seepage flow rate and sediment transport. Groundwater conditions were again monitored by the tensiometer and observation well network. Experiments consisted of a trench injection at a constant head and observations of flow rates, erosion rates, soil-water pressures, and water table elevations. Flow rates varied from 0.004 L/min to 1.16 L/min at different locations on the bank. It was observed that the seeps experienced ‘self-healing’ erosion in which upper layer cohesive soil failures blocked further particle mobilization. One experiment simulated fluvial erosion removing the failed material, thereby, resulting in combined erosion rates of over 6000 g/min. Seepage erosion could be a dominate mechanism of streambank failure where the self-healing process is not occurring.}, journal={2011 Louisville, Kentucky, August 7 - August 10, 2011}, publisher={American Society of Agricultural and Biological Engineers}, author={Midgley, Taber Leon and Fox, Garey A and Wilson, Glenn V and Heeren, Derek M and Simon, Andrew and Langendoen, Eddy J}, year={2011} }
 @inproceedings{midgley_fox_wilson_heeren_simon_langendoen_2011, title={Streambank erosion and instability induced by groundwater seepage}, volume={4}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-81255185841&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2011, ASABE 2011}, author={Midgley, T.L. and Fox, G.A. and Wilson, G.V. and Heeren, D.M. and Simon, A. and Langendoen, E.J.}, year={2011}, pages={3009–3029} }
 @article{white_storm_busteed_smolen_zhang_fox_2010, title={A quantitative phosphorus loss assessment tool for agricultural fields}, volume={25}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77957749798&partnerID=MN8TOARS}, DOI={10.1016/j.envsoft.2010.03.017}, abstractNote={In the United States, government sponsored conservation programs are under increasing pressure to quantify the environmental benefits of practices they subsidize. To meet this objective, conservation planners need tools to accurately predict phosphorus (P) loss from agricultural lands. Existing P export coefficient based tools are easy to use, but do not adequately account for local conditions. Hydrologic and water quality models are more accurate, but are prohibitively complex for conservation planners to use. Pasture Phosphorus Management (PPM) Plus was developed as a user-friendly P and sediment loss prediction tool based on the Soil and Water Assessment Tool (SWAT), a popular comprehensive hydrologic and water quality model. PPM Plus is applicable under a wide variety of management options and conservation practices and simple enough for use by conservation planners. SWAT hydrologic components were calibrated to allow application anywhere in the State of Oklahoma. The SWAT model was modified to include soil P algorithm updates and improved representation of conservation practices. This tool was successfully validated using 286 field years of measured data from the southern United States. PPM Plus allows the development of more effective conservation plans by allowing planners to evaluate pollutant losses resulting from a particular management strategy prior to implementation.}, number={10}, journal={Environmental Modelling and Software}, author={White, M.J. and Storm, D.E. and Busteed, P.R. and Smolen, M.D. and Zhang, H. and Fox, G.A.}, year={2010}, pages={1121–1129} }
 @inproceedings{mittelstet_heeren_storm_fox_white_miller_2010, title={Comparison of subsurface and surface runoff phosphorus transport capacities in alluvial floodplains}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79955450324&partnerID=MN8TOARS}, booktitle={ASABE - TMDL 2010: Watershed Management to Improve Water Quality}, author={Mittelstet, A.R. and Heeren, D.M. and Storm, D.E. and Fox, G.A. and White, M.J. and Miller, R.B.}, year={2010}, pages={142–150} }
 @inproceedings{fox_heeren_kizer_2010, title={Evaluation of alluvial well depletion analytical solutions from a stream-aquifer analysis test along the North Canadian River in Oklahoma}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77954964383&partnerID=MN8TOARS}, DOI={10.1061/41114(371)113}, abstractNote={Extracting ground water from pumping wells located adjacent to streams can reduce streamflow, a result that is known as alluvial well depletion. Primary factors influencing stream-aquifer interaction during alluvial well depletion are the hydrologic properties of the aquifer, the degree of penetration of the stream into the aquifer, and a potential streambed layer with a hydraulic conductivity different than the aquifer conductivity. Research over the past decade has developed analytical solutions for streams that account for more site-specific features but become mathematically complex. Evaluation of these analytical solutions using field data from multiple regions is needed to assess existing and recently proposed solutions' applicability and predictive capability. At a well site located adjacent to the North Canadian River in central Oklahoma, a stream-aquifer analysis test was performed. Observation wells were installed between the stream and the pumping well and were instrumented with automated water level sensors to measure water levels every 5 minutes. During the stream-aquifer analysis test, a discharge well located approximately 85 m from the North Canadian River was pumped at a constant rate (2180 m 3 /d) for 90 hrs. Predicted drawdown from several analytical solutions were fit to the measured drawdown to inversely estimate the aquifer transmissivity, T = 790 to 950 m 2 /d, specific yield, S y = 0.19 to 0.28, and streambed conductance, λ > 1500 m/d, and then to estimate stream depletion caused by the pumping well. The stream-aquifer analysis test suggested that the stream was behaving similar to a fully penetrating stream with streambed conductivity equivalent to the alluvial aquifer conductivity. For this system, simple analytical solutions were adequate to inversely estimate the aquifer and streambed hydrologic parameters, especially since early-time delayed yield effects were ignored. After only one day of pumping, estimated stream depletion ranged between 30 and 35% of the pumping rate. After five days of pumping, the estimated stream depletion was 60 to 70% of the pumping rate. These results highlight the intense degree of stream-aquifer interaction in this system, which should be accounted for in allocating future water rights.}, booktitle={World Environmental and Water Resources Congress 2010: Challenges of Change - Proceedings of the World Environmental and Water Resources Congress 2010}, author={Fox, G.A. and Heeren, D.M. and Kizer, M.A.}, year={2010}, pages={1030–1039} }
 @article{miller_heeren_fox_storm_halihan_mittelstet_2010, title={Geophysical Mapping of Preferential Flow Paths across Multiple Floodplains}, DOI={10.13031/2013.29715}, abstractNote={In the Ozark ecoregion of Oklahoma, Arkansas and Missouri, the erosion of carbonate bedrock (primarily limestone) by slightly acidic water has left a residuum of chert gravel, producing gravel-bed streams and floodplains generally consisting of coarse chert gravel overlain by a mantle (1 to 300 cm) of gravelly loam or silt loam. Previous research has documented the occurrence of preferential flow paths (PFP) in an alluvial floodplain hypothesized to be a buried gravel bar. Field experiments have shown that the PFP affected alluvial groundwater flow in the floodplain and that water flow in the PFP was transmitted at rates that limited sorption of phosphorus. The implication of these findings depends partly on the frequency and distribution of similar preferential flow features. To this end, four floodplain sites were chosen for comparative mapping. The sites were located in the Ozark region of northeast Oklahoma and had similar underlying geology but differed in watershed area, land cover, and stream order. Subsurface features at the sites were mapped using electrical resistivity imaging (ERI). Vadose zone hydraulic conductivity was measured at three sites using a direct-push borehole permeameter. The ERI profiles at each site showed that the subsurface was heterogeneous and areas of high electrical resistivity formed discrete, possibly continuous features in the vadose zone. Interpolations, based on variograms of resistivity, showed that resistivity within the alluvial aquifers formed patterns that were often linked to geomorphic processes. Hydraulic conductivity within the alluvial aquifers was estimated by applying an empirical linear relationship between electrical resistivity and hydraulic conductivity. Since all of the alluvial floodplain sites were gravel dominated systems, the sites were similar enough that the linear relationship between electrical resistivity and hydraulic conductivity was not site-specific. The positive slope of the relationship suggested that areas of continuous high resistivity could also act as zones of preferential flow within the aquifer under suitable hydrologic conditions. Among the sites, maximum electrical resistivity and hydraulic conductivity generally increased with increasing watershed area.}, journal={2010 Pittsburgh, Pennsylvania, June 20 - June 23, 2010}, publisher={American Society of Agricultural and Biological Engineers}, author={Miller, Ronald B and Heeren, Derek M and Fox, Garey A and Storm, Daniel E and Halihan, Todd and Mittelstet, Aaron R}, year={2010} }
 @inproceedings{miller_heeren_fox_storm_halihan_mittelstet_2010, title={Geophysical mapping of preferential flow paths across multiple floodplains}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78649711636&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2010, ASABE 2010}, author={Miller, R.B. and Heeren, D.M. and Fox, G.A. and Storm, D.E. and Halihan, T. and Mittelstet, A.R.}, year={2010}, pages={1898–1919} }
 @article{heeren_miller_fox_storm_mittelstet_penn_2010, title={Impact of Preferential Flow Paths on Alluvial Groundwater Flow Patterns and Phosphorus Transport}, DOI={10.13031/2013.29714}, abstractNote={While surface runoff is considered to be the primary transport mechanism for phosphorus (P), subsurface transport through coarse subsoil to gravel bed streams may be significant and represent a source of P not alleviated by current conservation practices (e.g., riparian buffers). Previous research has documented P transport in a preferential flow path (PFP) identified as a buried gravel bar. It is hypothesized that PFPs, if connected to the soil surface, provide a rapid and efficient method of transporting P, and that these alluvial features are transient storage zones for nutrients, acting as a sink during high flow and a source during baseflow. The objectives of this project were to document the impact of PFPs on groundwater flow patterns on a field scale and to quantify potential P transport capacity through PFPs. Long-term monitoring was performed at floodplain sites adjacent to Barren Fork Creek and Honey Creek in northeastern Oklahoma. Based on results from subsurface electrical resistivity mapping, observation wells were installed both in PFPs and in non-PFP subsoils. Water levels and temperature in the wells were monitored real-time using pressure transducers for four months, which included multiple high flow events. Also, P samples were obtained from the observation wells and in the stream to document P concentration gradients over time. Contour plots showing direction of flow were generated based on water table elevation data. Results indicated spatial heterogeneity in hydraulic conductivity and zones of groundwater convergence and divergence. The activity of PFPs depended on the elevation of the water table and the interaction between the stream and the groundwater. The PFPs that rapidly transported P had groundwater total P concentrations that mimicked the stream and exceeded 0.20 mg/L during some high flow events. The pathways with rapid P transport did not necessarily correlate to subsurface zones of high hydraulic conductivity. Pathways of high hydraulic conductivity must be connected to the surface water source and be hydraulically activated for preferential transport to occur.}, journal={2010 Pittsburgh, Pennsylvania, June 20 - June 23, 2010}, publisher={American Society of Agricultural and Biological Engineers}, author={Heeren, Derek M and Miller, Ron B and Fox, Garey A and Storm, Daniel E and Mittelstet, Aaron R and Penn, Chad J}, year={2010} }
 @inproceedings{heeren_miller_fox_storm_mittelstet_penn_2010, title={Impact of preferential flow paths on alluvial groundwater flow patterns and phosphorus transport}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78649708878&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2010, ASABE 2010}, author={Heeren, D.M. and Miller, R.B. and Fox, G.A. and Storm, D.E. and Mittelstet, A.R. and Penn, C.J.}, year={2010}, pages={1882–1897} }
 @inproceedings{heeren_miller_fox_storm_fox_mittelstet_2010, title={Impact of preferential flow paths on stream and alluvial groundwater interaction}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77955009499&partnerID=MN8TOARS}, DOI={10.1061/41114(371)114}, abstractNote={A better understanding of stream-aquifer interactions is needed both for water policy and for quantifying its impact on stream chemistry and water quality. Assuming homogeneity in alluvial aquifers is convenient but limits our understanding of stream-aquifer interactions. Previous research in the Ozark ecoregion, which is characterized by cherty soils and gravel bed streams, identified subsoils with hydraulic conductivities of 140 to 230 m d –1 and showed non-uniform groundwater flow. In a preferential flow path (PFP), even a sorbing contaminant, such as phosphorus, was found to be transported and not significantly attenuated through the subsurface. The objective of this research was to document the impact of flow heterogeneity (i.e., PFPs) on groundwater flow patterns, which will strengthen current understanding of contaminant interaction between streams and alluvial aquifers. Long term monitoring was performed adjacent to the Barren Fork Creek and Honey Creek in northeastern Oklahoma. Based on results from subsurface electrical resistivity mapping, observation wells were installed both in PFPs and in non-PFP subsoils. Water levels in the wells were recorded real-time using pressure transducers. Plots of the water table elevation, streamlines, and water level divergence were generated using six weeks of data including multiple high flow events. Divergence was used to quantify heterogeneity in hydraulic conductivity. The activity of PFPs depended on the elevation of the water table and the interaction between the stream and the groundwater. It appeared that PFPs acted as divergence zones, allowing stream water to quickly enter the groundwater system, or as flow convergence zones, draining a large groundwater area.}, booktitle={World Environmental and Water Resources Congress 2010: Challenges of Change - Proceedings of the World Environmental and Water Resources Congress 2010}, author={Heeren, D.M. and Miller, R.B. and Fox, G.A. and Storm, D.E. and Fox, A.K. and Mittelstet, A.R.}, year={2010}, pages={1040–1051} }
 @article{influence of flow concentration on parameter importance and prediction uncertainty of pesticide trapping by vegetative filter strips_2010, volume={384}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77649185792&partnerID=MN8TOARS}, DOI={10.1016/j.jhydrol.2010.01.020}, abstractNote={Flow concentration is a key hydrologic factor limiting the effectiveness of vegetated filter strips (VFS) in removing pesticides from surface runoff. Numerical models, such as VFSMOD-W, offer a mechanistic approach for evaluating VFS effectiveness under various hydrological conditions including concentrated flow. This research hypothesizes that the presence of concentrated flow drastically alters the importance of various hydrological, sedimentological, and pesticide input factors and the prediction uncertainty of pesticide reduction. Using data from a VFS experimental field study investigating chlorpyrifos and atrazine transport, a two-step global sensitivity and uncertainty analysis framework was used with VFSMOD-W based on (1) a screening method (Morris) and (2) a variance-based method (extended Fourier Analysis Sensitivity Test, FAST). The vertical, saturated hydraulic conductivity was consistently the most important input factor for predicting infiltration, explaining 49% of total output variance for uniform sheet flow, but only 8% for concentrated flow. Sedimentation was governed by both hydrologic (vertical, saturated hydraulic conductivity and initial and saturated water content) and sediment characteristics (average particle diameter). The vertical, saturated hydraulic conductivity was the most important input factor for atrazine or chlorpyrifos trapping under uniform sheet flow (explained more than 46% of the total output variance) and concentrated flow (although only explained 8% of the total variance in this case). The 95% confidence intervals for atrazine and chlorpyrifos reduction ranged between 43% and 78% for uniform sheet flow and decreased to between 1% and 16% under concentrated flow. Concentrated flow increased interactions among the system components, enhancing the relative importance of processes that were latent under shallow flow conditions. This complex behavior warrants the need for process-based modeling to be able to predict the performance of VFS under a wide range of specific hydrological conditions.}, number={1-2}, journal={Journal of Hydrology}, year={2010}, pages={164–173} }
 @article{fox_heeren_wilson_langendoen_fox_chu-agor_2010, title={Numerically predicting seepage gradient forces and erosion: Sensitivity to soil hydraulic properties}, volume={389}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77955050727&partnerID=MN8TOARS}, DOI={10.1016/j.jhydrol.2010.06.015}, abstractNote={Research has suggested that streambank seepage can be an important mechanism of bank instability; however, limited information is available on the level of soil characterization necessary to accurately predict seepage gradient forces and erosion. The objective of this research was to quantify the expected range of predicted seepage gradients for various degrees of site characterization. Uncertainty analysis on seepage gradient predictions was performed relative to variability in soil hydraulic properties. A two-dimensional unsaturated/saturated groundwater flow model was used to simulate a homogeneous soil layer for sand and loamy sand soils packed at various bulk densities, ρb. A pedotransfer function (ROSETTA), designed to estimate unsaturated hydraulic properties from surrogate soil data (i.e., texture and bulk density), was used to derive the saturated hydraulic conductivity, Ks, and water retention parameters for various levels of site information (i.e., only textural class; percent sand, silt, and clay (%SSC); %SSC and ρb; and %SSC, ρb, and Ks). Statistical distributions were derived for each soil hydraulic parameter and Monte Carlo simulations were performed to generate distributions of maximum seepage gradient. The deviation in predicted seepage gradient was calculated using assumed baseline conditions. Ranges in predicted soil hydraulic parameters and maximum seepage gradients were considerably reduced when using %SSC as compared to soil texture. Therefore, at a minimum, soil samples should be taken for particle size analysis. For ρb between 1450 and 1500 kg m−3, soil hydraulic parameters could be derived using ROSETTA and inputting %SSC, with little additional benefit provided by measuring ρb and/or Ks. When the ρb was less than 1450–1500 kg m−3, inputting ρb and/or Ks consistently reduced the magnitude of deviations from the baseline and therefore should be measured from undisturbed soil samples. The opposite was observed for ρb greater than 1450–1500 kg m−3 due to discrepancies between ROSETTA-derived and actual values of soil hydraulic parameters other than Ks. Considerable deviations (i.e., around 20%) were observed in seepage gradients under this scenario. When ROSETTA-derived and actual values of soil hydraulic parameters more closely matched, inputting ρb and/or Ks benefitted seepage gradient predictions as deviations in seepage gradients were less than 5% for the sand and loamy sand soils. Therefore, it is vital to quantify all soil hydraulic parameters for high ρb soils and textures with a wide range in %SSC.}, number={3-4}, journal={Journal of Hydrology}, author={Fox, G.A. and Heeren, D.M. and Wilson, G.V. and Langendoen, E.J. and Fox, A.K. and Chu-Agor, M.L.}, year={2010}, pages={354–362} }
 @article{fox_bellmer_elliott_2010, title={Option-Specific Program Outcomes to Meet Biological Engineering Program Criteria}, DOI={10.13031/2013.29733}, abstractNote={Program outcomes are defined by ABET as narrow statements that describe the skills that students should possess at the time of graduation. ABET specifies a set of outcomes that should be met by all engineering programs. In order to demonstrate that the curriculum adequately meets specific program criteria, one alternative is to define additional outcomes with respect to the program criteria. Many traditional agricultural engineering programs must now meet ABET-defined program criteria for biological engineering. While these departments are offering curricula aimed at achieving an advanced knowledge of biology, chemistry, and engineering sciences, departments may also wish to continue to offer agricultural engineering subject matter to meet the needs of their constituents. Within a single degree program, this creates an interesting merge between conventional agricultural engineering and modern biological engineering curricula. The objective of this paper is to demonstrate how one department is attempting to merge these emphases and satisfy ABET accreditation. The Biosystems Engineering program at Oklahoma State University attempts to meet both needs through four degree options. To meet the biological engineering program criteria and advanced knowledge of biology and chemistry in each option, option-specific outcome statements and performance criteria were defined. Each option-specific outcome states that students should have an ability to apply the physical, chemical, biological, and engineering sciences to solve problems at the interface of biology and engineering relative to the option’s emphasis. The program believes that this strategy appropriately recognizes the differential definition of “advanced biology and chemistry” and “a working knowledge of advanced biological sciences” in the curriculum. A two-tiered assessment approach is then used to assess required ABET outcomes and the program’s option-specific outcome. This approach appears to lessen additional work load on faculty members relative to accreditation while at the same time investigating specific details of any curriculum concerns that arise from assessment and evaluation.}, journal={2010 Pittsburgh, Pennsylvania, June 20 - June 23, 2010}, publisher={American Society of Agricultural and Biological Engineers}, author={Fox, Garey A and Bellmer, Danielle and Elliott, Ronald L}, year={2010} }
 @inproceedings{fox_bellmer_elliott_2010, title={Option-specific program outcomes to meet biological engineering program criteria}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78649698075&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2010, ASABE 2010}, author={Fox, G.A. and Bellmer, D. and Elliott, R.L.}, year={2010}, pages={2242–2248} }
 @article{muñoz-carpena_fox_sabbagh_2010, title={Parameter importance and uncertainty in predicting runoff pesticide reduction with filter strips}, volume={39}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77649207024&partnerID=MN8TOARS}, DOI={10.2134/jeq2009.0300}, abstractNote={Vegetative filter strips (VFS) are an environmental management tool used to reduce sediment and pesticide transport from surface runoff. Numerical models of VFS such as the Vegetative Filter Strip Modeling System (VFSMOD‐W) are capable of predicting runoff, sediment, and pesticide reduction and can be useful tools to understand the effectiveness of VFS and environmental conditions under which they may be ineffective. However, as part of the modeling process, it is critical to identify input factor importance and quantify uncertainty in predicted runoff, sediment, and pesticide reductions. This research used state‐of‐the‐art global sensitivity and uncertainty analysis tools, a screening method (Morris) and a variance‐based method (extended Fourier Analysis Sensitivity Test), to evaluate VFSMOD‐W under a range of field scenarios. The three VFS studies analyzed were conducted on silty clay loam and silt loam soils under uniform, sheet flow conditions and included atrazine, chlorpyrifos, cyanazine, metolachlor, pendimethalin, and terbuthylazine data. Saturated hydraulic conductivity was the most important input factor for predicting infiltration and runoff, explaining >75% of the total output variance for studies with smaller hydraulic loading rates (∼100–150 mm equivalent depths) and ∼50% for the higher loading rate (∼280‐mm equivalent depth). Important input factors for predicting sedimentation included hydraulic conductivity, average particle size, and the filter's Manning's roughness coefficient. Input factor importance for pesticide trapping was controlled by infiltration and, therefore, hydraulic conductivity. Global uncertainty analyses suggested a wide range of reductions for runoff (95% confidence intervals of 7–93%), sediment (84–100%), and pesticide (43–100%) . Pesticide trapping probability distributions fell between runoff and sediment reduction distributions as a function of the pesticides' sorption. Seemingly equivalent VFS exhibited unique and complex trapping responses dependent on the hydraulic and sediment loading rates, and therefore, process‐based modeling of VFS is required.}, number={2}, journal={Journal of Environmental Quality}, author={Muñoz-Carpena, R. and Fox, G.A. and Sabbagh, G.J.}, year={2010}, pages={630–641} }
 @article{heeren_miller_fox_storm_halihan_penn_2010, title={Preferential flow effects on subsurface contaminant transport in alluvial floodplains}, volume={53}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77949864756&partnerID=MN8TOARS}, number={1}, journal={Transactions of the ASABE}, author={Heeren, D.M. and Miller, R.B. and Fox, G.A. and Storm, D.E. and Halihan, T. and Penn, C.J.}, year={2010}, pages={127–136} }
 @article{sabbagh_fox_muñoz-carpena rafael_lenz_2010, title={Revised Framework for Pesticide Aquatic Environmental Exposure Assessment that Accounts for Vegetative Filter Strips}, volume={44}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es100506s}, DOI={10.1021/es100506s}, abstractNote={For pesticides that do not pass higher-level environmental exposure assessments, vegetated filter strips (VFS) are often mandated for use of the compound. However, VFS physiographic characteristics (i.e., width) are not currently specified based on predictive modeling of VFS performance. This has been due to the lack of predictive tools that can explain the wide range of field-reported efficacies. This research hypothesizes that mechanistic modeling of VFS runoff and sediment trapping, integrated with an empirical, regression-based pesticide trapping equation and the U.S. Environmental Protection Agency's (EPA) exposure framework, is able to effectively derive these VFS characteristics. To test this hypothesis, a well-tested process-based model for VFS (VFSMOD) was coupled with the pesticide trapping equation and integrated with EPA's PRZM/EXAMS exposure package. The revised framework was applied to a prescribed U.S. EPA assessment scenario for four hypothetical pesticides: more mobile (i.e., organic carbon (OC) sorption coefficients, K(oc), of 100 L/kg OC) and less mobile (2000 L/kg OC) pesticides that are fast degrading or stable (i.e., 10 or 10,000 d aquatic dissipation half-lives). A nonlinear and complex relationship was observed between pesticide reduction, VFS length, and rainfall plus runon event size. The impact of VFS on environmental exposure concentrations (EECs) was found to be dependent on the pesticide sorption and dissipation half-life and whether calculating an acute or chronic EEC. While acute and chronic EECs were equivalent for stable pesticides, for fast degrading pesticides the acute EEC depended on specific loading events. Therefore, while VFS may reduce the cumulative pesticide loading, a corresponding reduction in the acute EEC may not always be observed. Such results emphasize the need to incorporate physically based modeling of VFS reductions for pesticides that do not pass the current U.S. EPA exposure assessment framework.}, number={10}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Sabbagh, George J. and Fox, Garey A. and Muñoz-Carpena Rafael and Lenz, Mark F.}, year={2010}, month={May}, pages={3839–3845} }
 @inproceedings{niezgoda_carpenter_castro_curran_fox_hotchkiss_johnson_pomeroy_rosgen_schmidt_et al._2010, title={Stream restoration education and professional development: Working toward a consensus}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77954991588&partnerID=MN8TOARS}, DOI={10.1061/41114(371)192}, abstractNote={The rapid evolution of river restoration technology, in combination with the diversity of disciplines represented in the restoration field, has created ideal conditions for increased market demands for restoration short courses. Therefore, it is not surprising that there exist numerous short courses and certificate programs in stream restoration offered by private consulting firms, government agencies, nonprofit organizations and universities. These courses typically range from one day to week-long classes that introduce the student to basic concepts and principles of fluvial geomorphology and stream restoration. With an abundance of course offerings, it is problematic to determine what is being taught, who is teaching, to whom it is being delivered, and what is really being learned. There is growing concern that many short courses are offered as stand-alone entities, with no prerequisites and no assessment of learning. This can lead disconcertingly to over-confident, over-eager restorationists who do not fully appreciate the complexity and interdisciplinary nature of river restoration projects. In order to address these issues and meet an ever-growing need for restoration professional development, a stream restoration educational materials task committee (TC) of the River Restoration Committee of the ASCE-EWRI Hydraulics and Waterways Council was formed in May 2009. The goals of the TC are to provide the restoration community with (1) a recommended standard curriculum based on needs (technicians, engineers, planners, ecologists, biologists, etc.), (2) a list of educator traits most properly suited to cover that curriculum (not specific individuals or institutions), and (3) logistics of where and how to most effectively disseminate information. The objective of this paper is to present preliminary results from work completed by the TC, including a list of courses and outcomes (and level of cognition) that account for the insights of practicing engineers, needs of graduate programs, and pedagogical and personnel limitations of a specific program.}, booktitle={World Environmental and Water Resources Congress 2010: Challenges of Change - Proceedings of the World Environmental and Water Resources Congress 2010}, author={Niezgoda, S.L. and Carpenter, D. and Castro, J. and Curran, J. and Fox, G. and Hotchkiss, R. and Johnson, P.A. and Pomeroy, C. and Rosgen, D. and Schmidt, J. and et al.}, year={2010}, pages={1838–1849} }
 @article{guzman_fox_payne_2010, title={Surface Runoff Transport of Escherichia coli after Poultry Litter Application on Pastureland}, DOI={10.13031/2013.29713}, abstractNote={Escherichia coli transported in surface runoff from dissolution of applied poultry litter is a major variable in assessing fecal contamination of streams. However, the relative magnitude of the E. coli concentration from a specific poultry litter application and relative to the time lag between litter application and rainfall are not completely understood. This research investigated E. coli transport in runoff on fourteen, 2 m by 2 m pastureland plots. Poultry litter was manually applied (4,942 kg/ha) in twelve plots followed by artificial rainfall with intensities equivalent to 2-yr and 5-yr storm events. Rainfall was applied in duplicate plots immediately after poultry litter application and 24 and 120 hr after litter application. Experiments were also conducted on two control plots without poultry litter application. Surface runoff was collected using a flume installed in a trench. Escherichia coli was quantified from sampled runoff and used as an indicator of fecal contamination by the most probable number (MPN) technique. No significant differences were observed in average event mean concentrations (EMCs) relative to storm intensity. Statistically significant differences were observed in average EMCs relative to time lag between litter application and rainfall. A nonlinear relationship was observed between average Escherichia coli EMC and time lag, with the EMC decreasing between 0 hr (1.6x105 MPN/100 mL) and 24 hr (1.3x104 MPN/100 mL) and then increasing at 120 hr (4.3x104 MPN/100 mL). Escherichia coli were always detected in the control plots (average EMC of 6.8x103 MPN/100 mL) indicating the presence and transport of fecal bacteria from sources independent of the immediate poultry litter application. Even though poultry litter application may increase E. coli concentrations in runoff, other sources of fecal contamination serve as a significant component of the total E. coli EMC, especially as the time lag between litter application and rainfall events increase.}, journal={2010 Pittsburgh, Pennsylvania, June 20 - June 23, 2010}, publisher={American Society of Agricultural and Biological Engineers}, author={Guzman, Jorge A and Fox, Garey A and Payne, Josh B}, year={2010} }
 @inproceedings{guzman_fox_payne_2010, title={Surface runoff transport of Escherichia coli after poultry litter application on pastureland}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78649703466&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2010, ASABE 2010}, author={Guzman, J.A. and Fox, G.A. and Payne, J.B.}, year={2010}, pages={1867–1881} }
 @article{guzman_fox_payne_2010, title={Surface runoff transport of Escherichia coli after poultry litter application on pastureland}, volume={53}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77954091110&partnerID=MN8TOARS}, number={3}, journal={Transactions of the ASABE}, author={Guzman, J.A. and Fox, G.A. and Payne, J.B.}, year={2010}, pages={779–786} }
 @article{fox_wilson_2010, title={The Role of Subsurface Flow in Hillslope and Stream Bank Erosion: A Review}, volume={74}, url={http://dx.doi.org/10.2136/sssaj2009.0319}, DOI={10.2136/sssaj2009.0319}, abstractNote={Sediment is one of the most common causes of stream impairment. Great progress has been made in understanding the processes of soil erosion due to surface runoff and incorporating these in prediction technologies. In many landscapes, however, the dominant source of sediment is derived from mass wasting of hillslopes and stream banks, potentially driven by subsurface flow. We highlight the mechanisms and importance of subsurface flow processes in erosion associated with hillslopes and stream banks. Subsurface flow affects erosion directly by seepage and pipe flow processes and indirectly by the relationship of soil properties with soil water pressure. Seepage contributes to erosion through interrelated mechanisms: hydraulic gradient forces that reduce the resistance of the particle to dislodging from the soil matrix and particle mobilization when soil particles become entrained in exfiltrating water. Preferential flow through soil pipes results in internal erosion of the pipe, which may produce gullies by tunnel collapse. The eroded material can clog soil pipes, causing pore water pressure buildup inside the pipes that can result in landslides, debris flows, embankment failures, or reestablishment of ephemeral gullies. Research in the past decades has advanced our understanding of these processes, leading to mathematical relationships that can be incorporated into mechanistic, process‐based models. Further research advances are necessary, however, especially on the complexity of the interactive effects of surface flow, seepage, pipe flow, and vegetation on soil erosion properties. More information is needed on the extent that subsurface flow contributes to hillslope and stream bank erosion. We believe that multidisciplinary efforts between soil scientists, geotechnical engineers, hydraulic engineers, and hydrologists are necessary to fully understand and integrate subsurface flow and soil erosion processes in simulation tools.}, number={3}, journal={Soil Science Society of America Journal}, author={Fox, G.A. and Wilson, G.V.}, year={2010}, month={May}, pages={717–733} }
 @inproceedings{miller_heeren_fox_halihan_storm_mittelstet_2010, title={Use of multi-electrode resistivity profiling to estimate hydraulic properties of preferential flow paths in alluvial floodplains}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77955008149&partnerID=MN8TOARS}, DOI={10.1061/41114(371)106}, abstractNote={The Ozark region of eastern Oklahoma is characterized by limestone and sandstone plateaus partitioned by steep-sided stream valleys and occupied by clear, gravel-bed streams. Alluvial floodplain soils are generally cherty with high hydraulic conductivities. Many areas have alluvial floodplains consisting of a mantle of alluvial soils overlying thick subsoil primarily consisting of gravel. Previous work at a site in eastern Oklahoma found preferential flow of a conservative tracer within the gravel subsoil with an estimated hydraulic conductivity of 140 to 230 m/d. Multi-electrode electrical resistivity imaging (ERI) was used as a non-invasive method to determine the nature and extent of the preferential flow path (PFP). The ERI two-dimensional profile found a highly resistive layer in the area of the PFP. The range of resistance for this area was similar to the resistance found in an ERI survey from the surface of a nearby gravel bar, which strongly suggested that the PFP consists of clean, coarse gravel. This study attempted to determine whether PFPs exist at two other alluvial floodplain sites in the Ozarks with differing catchment areas. Since the factors controlling resistivity are similar to the factors controlling hydraulic conductivity, an association between the two was expected. Borehole permeameter tests, using a system specifically designed for gravelly soils, were used to estimate saturated hydraulic conductivity. An equation was developed between the point-measured hydraulic conductivity and larger-scale electrical resistivity mapping. Limitations in current analytical solutions prevented the estimation of hydraulic conductivity for all tests, primarily due to the rates that were induced on the gravel subsoils.}, booktitle={World Environmental and Water Resources Congress 2010: Challenges of Change - Proceedings of the World Environmental and Water Resources Congress 2010}, author={Miller, R.B. and Heeren, D.M. and Fox, G.A. and Halihan, T. and Storm, D.E. and Mittelstet, A.R.}, year={2010}, pages={959–969} }
 @inproceedings{chu-agor_fox_wilson_2009, title={A seepage erosion sediment transport function and geometric headcut relationships for predicting seepage erosion undercutting}, volume={342}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70350164430&partnerID=MN8TOARS}, DOI={10.1061/41036(342)378}, abstractNote={Seepage erosion is an important factor in hillslope instability and failure. However, predicting erosion by subsurface flow or seepage and incorporating its effects into stability models remain a challenge. Limitations exist with all existing seepage erosion sediment transport functions, including neglecting the three-dimensional geometry of the seepage undercut. The objective was to develop a sediment transport model that can predict sediment mobilization (i.e., seepage erosion and undercutting) with time based on previously reported three-dimensional soil block experiments covering a wide range of hydraulic, soil type, and packing (i.e., slope and bulk density) combinations. The transport function was represented by an excess velocity equation wherein the rate of erosion was related to the difference between the steady state velocity and the critical velocity (R2 = 0.62). The critical velocity was derived from a critical head measured in the laboratory using the three-dimensional soil block. The relationship between the eroded volume per bank face area and the amplitude of the headcut was also derived. Using a three-dimensional Gaussian function, the geometric relationships between the lateral and vertical dimensions of the headcut were then estimated. Linear regression analysis between the predicted and observed time at which a given amount of headcut developed resulted in an R2 of 0.86. The ground water velocity exfiltrating a hillslope can be used with the derived sediment transport function to predict the dimensions of the headcut and the geometry of the undercut which enables the prediction of the impact of seepage erosion undercutting on hillslope stability.}, booktitle={Proceedings of World Environmental and Water Resources Congress 2009 - World Environmental and Water Resources Congress 2009: Great Rivers}, author={Chu-Agor, M.L. and Fox, G.A. and Wilson, G.V.}, year={2009}, pages={3763–3772} }
 @article{poletika_coody_fox_sabbagh_dolder_white_2009, title={Chlorpyrifos and atrazine removal from runoff by vegetated filter strips: Experiments and predictive modeling}, volume={38}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-66649116382&partnerID=MN8TOARS}, DOI={10.2134/jeq2008.0404}, abstractNote={Runoff volume and flow concentration are hydrological factors that limit effectiveness of vegetated filter strips (VFS) in removing pesticides from surface runoff. Empirical equations that predict VFS pesticide effectiveness based solely on physical characteristics are insufficient on the event scale because they do not completely account for hydrological processes. This research investigated the effect of drainage area ratio (i.e., the ratio of field area to VFS area) and flow concentration (i.e., uniform versus concentrated flow) on pesticide removal efficiency of a VFS and used these data to provide further field verification of a recently proposed numerical/empirical modeling procedure for predicting removal efficiency under variable flow conditions. Runoff volumes were used to simulate drainage area ratios of 15:1 and 30:1. Flow concentration was investigated based on size of the VFS by applying artificial runoff to 10% of the plot width (i.e., concentrated flow) or the full plot width (i.e., uniform flow). Artificial runoff was metered into 4.6‐m long VFS plots for 90 min after a simulated rainfall of 63 mm applied over 2 h. The artificial runoff contained sediment and was dosed with chlorpyrifos and atrazine. Pesticide removal efficiency of VFS for uniform flow conditions (59% infiltration; 88% sediment removal) was 85% for chlorpyrifos and 62% for atrazine. Flow concentration reduced removal efficiencies regardless of drainage area ratio (i.e., 16% infiltration, 31% sediment removal, 21% chlorpyrifos removal, and 12% atrazine removal). Without calibration, the predictive modeling based on the integrated VFSMOD and empirical hydrologic‐based pesticide trapping efficiency equation predicted atrazine and chlorpyrifos removal efficiency under uniform and concentrated flow conditions. Consideration for hydrological processes, as opposed to statistical relationships based on buffer physical characteristics, is required to adequately predict VFS pesticide trapping efficiency.}, number={3}, journal={Journal of Environmental Quality}, author={Poletika, N.N. and Coody, P.N. and Fox, G.A. and Sabbagh, G.J. and Dolder, S.C. and White, J.}, year={2009}, pages={1042–1052} }
 @article{fox_sabbagh_2009, title={Comment on "major factors influencing the efficacy of vegetated buffers on sediment trapping: A review and analysis," by Xingmei Liu, Xuyang Zhang, and Minghua Zhang the Journal of Environmental Quality 2008 37:1667-1674}, volume={38}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-58349093105&partnerID=MN8TOARS}, DOI={10.2134/jeq2009.0001le}, abstractNote={Journal of Environmental QualityVolume 38, Issue 1 p. 1-3 Letter to the Editor Comment on “Major Factors Influencing the Efficacy of Vegetated Buffers on Sediment Trapping: A Review and Analysis,” by Xingmei Liu, Xuyang Zhang, and Minghua Zhang in the Journal of Environmental Quality 2008 37:1667–1674 Garey A. Fox, Corresponding Author Garey A. Fox garey.fox@okstate.edu Dep. of Biosystems and Agricultural Engineering, Oklahoma State Univ., Stillwater, OK, 74074garey.fox@okstate.edu, george.sabbagh@bayercropscience.comSearch for more papers by this authorGeorge J. Sabbagh, Corresponding Author George J. Sabbagh george.sabbagh@bayercropscience.com Bayer CropScience and Texas A&M Univ., 17745 South Metcalf, Stilwell, KS, 66085garey.fox@okstate.edu, george.sabbagh@bayercropscience.comSearch for more papers by this author Garey A. Fox, Corresponding Author Garey A. Fox garey.fox@okstate.edu Dep. of Biosystems and Agricultural Engineering, Oklahoma State Univ., Stillwater, OK, 74074garey.fox@okstate.edu, george.sabbagh@bayercropscience.comSearch for more papers by this authorGeorge J. Sabbagh, Corresponding Author George J. Sabbagh george.sabbagh@bayercropscience.com Bayer CropScience and Texas A&M Univ., 17745 South Metcalf, Stilwell, KS, 66085garey.fox@okstate.edu, george.sabbagh@bayercropscience.comSearch for more papers by this author First published: 01 January 2009 https://doi.org/10.2134/jeq2009.0001leCitations: 20 All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume38, Issue1January 2009Pages 1-3 RelatedInformation}, number={1}, journal={Journal of Environmental Quality}, author={Fox, G.A. and Sabbagh, G.J.}, year={2009}, pages={1–2} }
 @article{garbrecht_fox_guzman_alexander_2009, title={E. coli transport through soil columns: Implications for bioretention cell removal efficiency}, volume={52}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-67049155673&partnerID=MN8TOARS}, number={2}, journal={Transactions of the ASABE}, author={Garbrecht, K. and Fox, G.A. and Guzman, J.A. and Alexander, D.}, year={2009}, pages={481–486} }
 @article{sabbagh_fox_kamanzi_roepke_tang_2009, title={Effectiveness of vegetative filter strips in reducing pesticide loading: Quantifying pesticide trapping efficiency}, volume={38}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-58349121897&partnerID=MN8TOARS}, DOI={10.2134/jeq2008.0266}, abstractNote={Pesticide trapping efficiency of vegetated filter strips (VFS) is commonly predicted with low success using empirical equations based solely on physical characteristics such as width and slope. The objective of this research was to develop and evaluate an empirical model with a foundation of VFS hydrological, sedimentological, and chemical specific parameters. The literature was reviewed to pool data from five studies with hypothesized significant parameters: pesticide and soil properties, percent reduction in runoff volume (i.e., infiltration) and sedimentation, and filter strip width. The empirical model was constructed using a phase distribution parameter, defined as the ratio of pesticide mass in dissolved form to pesticide mass sorbed to sediment, along with the percent infiltration, percent sedimentation, and the percent clay content (R2 = 0.86 and standard deviation of differences [STDD] of 7.8%). Filter strip width was not a statistically significant parameter in the empirical model. For low to moderately sorbing pesticides, the phase distribution factor became statistically insignificant; for highly sorbing pesticides, the phase distribution factor became the most statistically significant parameter. For independent model evaluation datasets, the empirical model based on infiltration and sediment reduction, the phase distribution factor, and the percent clay content (STDD of 14.5%) outperformed existing filter strip width equations (STDD of 38.7%). This research proposed a procedure linking a VFS hydrologic simulation model with the proposed empirical trapping efficiency equation. For datasets with sufficient information for the VFS modeling, the linked numerical and empirical models significantly (R2 = 0.74) improved predictions of pesticide trapping over empirical equations based solely on physical VFS characteristics.}, number={2}, journal={Journal of Environmental Quality}, author={Sabbagh, G.J. and Fox, G.A. and Kamanzi, A. and Roepke, B. and Tang, J.-Z.}, year={2009}, pages={762–771} }
 @article{chu-agor_fox_wilson_2009, title={Empirical sediment transport function predicting seepage erosion undercutting for cohesive bank failure prediction}, volume={377}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70349289822&partnerID=MN8TOARS}, DOI={10.1016/j.jhydrol.2009.08.020}, abstractNote={Seepage erosion is an important factor in hillslope instability and failure. However, predicting erosion by subsurface flow or seepage and incorporating its effects into stability models remains a challenge. Limitations exist with all existing seepage erosion sediment transport functions, including neglecting the three-dimensional geometry of the seepage undercut and the cohesive nature of soils. The objective was to develop an empirical sediment transport function that can predict seepage erosion and undercutting with time based on three-dimensional soil block experiments covering a wide range of hydraulic, soil type, slope and bulk density combinations. The transport function was represented by an excess gradient equation (R2 = 0.54). The critical gradient was predicted by the soil cohesion based on laboratory experiments. Using a three-dimensional Gaussian function, the geometric relationships between the maximum distance and lateral and vertical dimensions of the undercut were then derived. The proposed empirical relationships reasonably predicted the observed volume per unit area of undercut, erosion rate, and time at which a given amount of undercut developed. The flow gradient can be used with the derived sediment transport function, the first ever relationship proposed for predicting the dimensions and the geometry of the undercut, to predict the impact of seepage erosion undercutting on hillslope stability. Users only need to input the seepage layer's cohesion, bulk density, and the hydraulic gradient over time in the near-bank ground water system.}, number={1-2}, journal={Journal of Hydrology}, author={Chu-Agor, M.L. and Fox, G.A. and Wilson, G.V.}, year={2009}, pages={155–164} }
 @article{guzman_fox_malone_kanwar_2009, title={Escherichia coli transport from surface-applied manure to subsurface drains through artificial biopores}, volume={38}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70350706102&partnerID=MN8TOARS}, DOI={10.2134/jeq2009.0077}, abstractNote={Bacteria transport in soils primarily occurs through soil mesopores and macropores (e.g., biopores and cracks). Field research has demonstrated that biopores and subsurface drains can be hydraulically connected. This research was conducted to investigate the importance of surface connected and disconnected (buried) biopores onEscherichia coli(E. coli) transport when biopores are located near subsurface drains. A soil column (28 by 50 by 95 cm) was packed with loamy sand and sandy loam soils to bulk densities of 1.6 and 1.4 Mg m−3, respectively, and containing an artificial biopore located directly above a subsurface drain. The sandy loam soil was packed using two different methods: moist soil sieved to 4.0 mm and air‐dried soil manually crushed and then sieved to 2.8 mm. A 1‐cm constant head was induced on the soil surface in three flushes: (i) water, (ii) diluted liquid swine (Sus scrofa) manure 48 h later, and (iii) water 48 h after the manure.Escherichia colitransport to the drain was observed with either open surface connected or buried biopores. In surface connected biopores,E. colitransport was a function of the soil type and the layer thickness between the end of the biopore and drain. Buried biopores contributed flow andE. coliin the less sorptive soil (loamy sand) and the sorptive soil (sandy loam) containing a wide (i.e., with mesopores) pore space distribution prevalent due to the moist soil packing technique. Biopores provide a mechanism for rapidly transportingE. coliinto subsurface drains during flow events.}, number={6}, journal={Journal of Environmental Quality}, author={Guzman, J.A. and Fox, G.A. and Malone, R.W. and Kanwar, R.S.}, year={2009}, pages={2412–2421} }
 @article{chu-agor_fox_wilson_2009, title={Incorporating Seepage Processes into a Streambank Stability Model}, DOI={10.13031/2013.27001}, abstractNote={Seepage processes are usually neglected in bank stability analyses although they can become a prominent failure mechanism under certain field conditions. This study incorporated the effects of seepage (i.e., seepage gradient forces and seepage erosion undercutting) into the Bank Stability and Toe Erosion Model (BSTEM) and evaluated the importance of the seepage mechanisms on bank stability. The effects of the seepage force were incorporated into BSTEM by modifying the force balance. Seepage erosion undercutting was simulated using a recently proposed sediment transport function. The modified BSTEM was then used to evaluate the stability of a streambank along Little Topashaw Creek under different scenarios: (1) without seepage forces and undercutting, (2) with seepage forces only, (3) with seepage undercutting only, and (4) with both seepage forces and undercutting. For a condition where the bank was fully saturated, the factor of safety (FS) decreased by as much as 66% (i.e., FS decreased from 2.68 to 0.91) from that of a dry condition due to the decrease in the frictional strength of the soil as the pore-water pressure increased. Incorporating the effects of the seepage force resulted in an average decrease in the FS of approximately 30 to 50% for all water table depths. Seepage erosion undercutting reduced the FS by approximately 6% for a 5 cm undercut (i.e., 2% of the bank height) and 11% for a 10 cm undercut (i.e., 3.3% of the bank height) due to the loss of supporting material in the conductive layer. Seepage erosion undercutting required 15 to 20 cm of seepage undercut to become the dominant failure mechanism over seepage forces and pore-water pressure effects. The cumulative effects of seepage reduced this streambank’s FS by up to 63% when the water table reached the entire bank height. The development of a bank stability model capable of simulating seepage processes was necessary in order to better understand site-specific failure mechanisms.}, journal={2009 Reno, Nevada, June 21 - June 24, 2009}, publisher={American Society of Agricultural and Biological Engineers}, author={Chu-Agor, Maria and Fox, Garey A and Wilson, Glenn V}, year={2009} }
 @inproceedings{chu-agor_fox_wilson_2009, title={Incorporating seepage processes into a streambank stability model}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-76549083520&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2009, ASABE 2009}, author={Chu-Agor, M.L. and Fox, G.A. and Wilson, G.}, year={2009}, pages={1769–1779} }
 @inproceedings{heeren_fox_chu-agor_wilson_2009, title={Predicting streambank seepage flows: Sensitivity to soil properties and layering}, volume={342}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70350139520&partnerID=MN8TOARS}, DOI={10.1061/41036(342)377}, abstractNote={Streambank failures result in loss of land and increased stream sediment loads. Variably saturated flow models integrated with bank stability models are being used to predict bank failure; however, understanding of the level of soil characterization necessary to predict when seepage contributes to bank failure is needed. ROSETTA, a pedotransfer function, was used to estimate hydraulic parameters for various levels of soil data (from texture class to saturated hydraulic conductivity, Ks). A two-dimensional groundwater flow code, SEEP/W, was used to model a hypothetical streambank and estimate seepage velocity. Results suggested that Ks and/or percent clay measurements are necessary to adequately predict seepage. A layered bank was also simulated with several combinations of soil types. Results indicated that only one order of magnitude difference in Ks (equivalent to a resistance ratio of 10) may be necessary to induce perching and seepage from the top layer. This research suggested that, if a field reconnaissance is performed to locate streambanks susceptible to perching, Ks and/or bulk density measurements are necessary to indicate the presence of a restrictive layer.}, booktitle={Proceedings of World Environmental and Water Resources Congress 2009 - World Environmental and Water Resources Congress 2009: Great Rivers}, author={Heeren, D.M. and Fox, G.A. and Chu-Agor, M.L. and Wilson, G.V.}, year={2009}, pages={3753–3762} }
 @article{heeren_miller_fox_storm_penn_halihan_2009, title={Preferential Flow Path Effects on Subsurface Contaminant Transport in Alluvial Floodplains}, DOI={10.13031/2013.27025}, abstractNote={For strongly sorbing contaminants, transport from upland areas to surface water systems is typically considered to be due to surface runoff with subsurface transport assumed negligible. However, certain local conditions can lead to an environment where subsurface transport to streams may be significant, a source of contamination not alleviated by current best management practices (e.g. riparian buffers). The Ozark region, including parts of Oklahoma, Arkansas, and Missouri, is characterized by cherty, gravelly soils and gravel bed streams. Previous research identified a preferential flow path (PFP) at a field site along the Barren Fork Creek in northeastern Oklahoma. With the subsoils having hydraulic conductivities on the order of 100 to 500 m/d, the previous research demonstrated that even a sorbing contaminant such as phosphorus can be transported in significant quantities through the subsurface. The objective of the current project was to determine the connectivity of the PFP to the stream and to further evaluate the hypothesis that the alluvial groundwater acts as a transient storage zone, providing a contaminant sink during high flow and a contaminant source during baseflow. A trench was installed above the PFP with the bottom of the trench at the topsoil/alluvial gravel interface. Piezometers were installed along the PFP and throughout the riparian floodplain, which was mapped with electrical resistivity equipment. Water was pumped into the trench to maintain a constant head, and a conservative tracer (Rhodamine WT) was injected into the trench. Water table elevations were recorded real-time using water level loggers and water samples were collected throughout the experiment. Results of the experiment demonstrated preferential movement of Rhodamine WT along the perched preferential flow pathway, infiltration of Rhodamine WT into the alluvial groundwater system, and then transport in the alluvial system as influenced by the stream/aquifer dynamics. This research demonstrated the importance of physical heterogeneity in affecting contaminant transport even in coarse gravel, alluvial subsoils.}, journal={2009 Reno, Nevada, June 21 - June 24, 2009}, publisher={American Society of Agricultural and Biological Engineers}, author={Heeren, Derek M and Miller, Ron B and Fox, Garey A and Storm, Daniel E and Penn, Chad J and Halihan, Todd}, year={2009} }
 @inproceedings{heeren_miller_fox_storm_penn_halihan_2009, title={Preferential flow path effects on subsurface contaminant transport in alluvial floodplains}, volume={4}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-76449101727&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2009, ASABE 2009}, author={Heeren, D.M. and Miller, R.B. and Fox, G.A. and Storm, D.E. and Penn, C.J. and Halihan, T.}, year={2009}, pages={2167–2176} }
 @book{hoang_pederson_kanwar_fox_2009, title={Role of Directly Connected Macropores on Pathogen Transport to Subsurface Drainage Water}, url={http://dx.doi.org/10.31274/farmprogressreports-180814-1242}, DOI={10.31274/farmprogressreports-180814-1242}, abstractNote={Pathogen contamination of water supplies is now considered one of the top water quality issues in the United States and worldwide. Continual application of livestock manure may contribute to nonpoint source pollution by releasing microbial pathogens including bacteria, virus, and protozoa, through runoff and subsurface drainage water to surface and ground water. Many studies have been conducted in the laboratories and fields to understand the preferential flow through macropores. But no experiments in the field have been conducted to examine the breakthrough curve of pathogen and/or Escherichia coliform (E.coli) with directly connected macropores. The objective of this research is to address the transport of pathogens (specifically the indicator organism E. coli) through soils, and more specifically the role of macropores in the transport of E. coli to subsurface drains. A greater understanding and more theoretical modeling approach is needed to understand the role of directly connected macropores on pathogen transport to subsurface drainage.}, number={RFR-A9116RFR-A9116}, institution={Iowa State University, Digital Repository}, author={Hoang, Chi Kim and Pederson, Carl H. and Kanwar, Rameshwar S. and Fox, Garey}, year={2009} }
 @article{lindow_fox_evans_2009, title={Seepage erosion in layered stream bank material}, volume={34}, ISSN={["1096-9837"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70349884157&partnerID=MN8TOARS}, DOI={10.1002/esp.1874}, abstractNote={Abstract}, number={12}, journal={EARTH SURFACE PROCESSES AND LANDFORMS}, author={Lindow, Nick and Fox, Garey A. and Evans, Robert O.}, year={2009}, month={Sep}, pages={1693–1701} }
 @article{guzman_fox_penn_2009, title={Sorption of E. coli from liquid swine manure in natural and artificial soils}, DOI={10.13031/2013.27091}, abstractNote={Animal waste applications in agricultural lands can contribute microbial contamination to water bodies. After manure application, Escherichia Coli (E. coli) can be transported by surface runoff and infiltration or can be retained in soils by its filter capacity. The soil filter capacity is a dynamic function of the physical-chemical properties of the soil, effluent composition and bacteria properties. In this study, E. coli isotherms were determined after mixing natural and artificial soils with manure effluents at different dilution ratios and decanting the clay particles by centrifugation. Two natural soils (e.g., loamy sand and sandy loam) and seven artificial soils were used with different clay (e.g., kaolinite: KGa-1) and organic matter (e.g., Sphagnum peat moss) content. In addition, the organic matter in the natural soils was removed using a hydrogen peroxide reagent. Sorption data fit a nonlinear Freundlich isotherm with a coefficient of determination, R2, higher than 0.93 except for the pure sand and natural soils after the organic matter was removed (e.g., R2 was higher than 0.84). Sorption data suggested that the presence of organic matter favored E. coli sorption in soils with clay contents lower than 10%. Sorption equations based on clay content without considering the effect of organic matter may underestimate E. coli sorption for varying solution E. coli concentrations. A general equation to estimate the Freundlich coefficients were obtained from the experiments based on the natural logarithms of clay content for total carbon content in the range of 0 to 2.1%. These equations are intended to be valuable in estimating E. coli sorption in manure-amended soils for improved modeling of E. coli fate and transport in soils.}, journal={2009 Reno, Nevada, June 21 - June 24, 2009}, publisher={American Society of Agricultural and Biological Engineers}, author={Guzman, Jorge A and Fox, Garey A and Penn, Chad J}, year={2009} }
 @inproceedings{guzmán_fox_penn_2009, title={Sorption of E. coli from liquid swine manure in natural and artificial soils}, volume={5}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-76549101418&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2009, ASABE 2009}, author={Guzmán, J.A. and Fox, G. and Penn, C.}, year={2009}, pages={3094–3104} }
 @article{fuchs_fox_storm_penn_brown_2009, title={Subsurface transport of phosphorus in riparian floodplains: Influence of preferential flow paths}, volume={38}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-63449114948&partnerID=MN8TOARS}, DOI={10.2134/jeq2008.0201}, abstractNote={For phosphorus (P) transport from upland areas to surface water systems, the primary transport mechanism is typically considered to be surface runoff with subsurface transport assumed negligible. However, certain local conditions can lead to an environment where subsurface transport may be significant. The objective of this research was to determine the potential of subsurface transport of P along streams characterized by cherty or gravel subsoils, especially the impact of preferential flow paths on P transport. At a field site along the Barren Fork Creek in northeastern Oklahoma, a trench was installed with the bottom at the topsoil/alluvial gravel interface. Fifteen piezometers were installed surrounding the trench to monitor flow and transport. In three experiments, water was pumped into the trench from the Barren Fork Creek to maintain a constant head. At the same time, a conservative tracer (Rhodamine WT) and/or potassium phosphate solution were injected into the trench at concentrations at 3 and 100 mg/L for Rhodamine WT and at 100 mg/L for P. Laboratory flow‐cell experiments were also conducted on soil material <2 mm in size to determine the effect that flow velocity had on P sorption. Rhodamine WT and P were detected in some piezometers at equivalent concentrations as measured in the trench, suggesting the presence of preferential flow pathways and heterogeneous interaction between streams and subsurface transport pathways, even in nonstructured, coarse gravel soils. Phosphorus transport was retarded in nonpreferential flow paths. Breakthrough times were approximately equivalent for Rhodamine WT and P suggesting no colloidal‐facilitated P transport. Results from laboratory flow‐cell experiments suggested that higher velocity resulted in less P sorption for the alluvial subsoil. Therefore, differences in flow rates between preferential and nonpreferential flow pathways in the field led to variable sorption. The potential for nutrient subsurface transport shown by this alluvial system has implications regarding management of similar riparian floodplain systems.}, number={2}, journal={Journal of Environmental Quality}, author={Fuchs, J.W. and Fox, G.A. and Storm, D.E. and Penn, C.J. and Brown, G.O.}, year={2009}, pages={473–484} }
 @inproceedings{guzman_fox_penn_2009, place={St. Joseph, Michigan}, title={The influence of organic matter on E. coli soil sorption}, booktitle={Proceedings of the ASABE Annual International Conference: 2009 Reno, Nevada, June 21 - June 24, 2009.}, publisher={American Society of Agricultural and Biological Engineers}, author={Guzman, J. and Fox, G.A. and Penn, C.J.}, year={2009} }
 @inproceedings{mittelstet_smolen_fox_2009, title={Using MODFLOW to compare management alternatives for a river alluvial aquifer}, volume={9}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77649083165&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2009, ASABE 2009}, author={Mittelstet, A. and Smolen, M. and Fox, G.}, year={2009}, pages={5917–5928} }
 @inproceedings{langendoen_wilson_fox_2008, place={Virginia Beach, Virginia}, title={Assessing the Impact of Riparian Soil-Water Dynamics on Streambank Erosion}, booktitle={Riparian Ecosystems and Buffers: Working at the Water's Edge, Proceedings 2008 AWRA Summer Specialty Conference}, author={Langendoen, E.J. and Wilson, G.V. and Fox, G.A.}, editor={Okay, J. and Todd, A.Editors}, year={2008} }
 @inproceedings{fox_kanwar_guzman_hoang_malone_moorman_pederson_2008, title={E. coli fate and transport in macroporous soils: Short-circuiting to the subsurface}, volume={316}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79251529167&partnerID=MN8TOARS}, DOI={10.1061/40976(316)32}, abstractNote={Pathogen concentrations in streamflow are commonly reported as a significant cause of water quality degradation throughout the world. Research has begun to attempt to model pathogen fate and transport, primarily through surface runoff mechanisms. A significant component of pathogen movement to streams commonly identified but not explicitly simulated in many models is pathogen movement to the subsurface, which can be important in several scenarios such as tile drainage systems. As colloidal contaminants, pathogens such as E. coli tend to become physically trapped in the soil matrix but can move quickly through soil macropores. In fact, concerns exist about the rapid transport of contaminants, such as pesticides, pathogens, and nutrients, from the soil surface to ground water through macropores. Recent research suggests short-circuiting or direct hydrologic connectivity between macropores and subsurface drains. The objective of this paper is to provide an overview of the current research regarding the fate and transport of E. coli through soil macropores and into subsurface drain systems. This paper reports early results from the first year of a multi-year study funded by the USDA Cooperative State Research, Education, and Extension Service as part of the their National Research Initiative program. Field experiments to document short-circuiting by macropores are described and also laboratory data is presented from soil column experiments, capable of simulating surface-connected macropores, with artificial subsurface drainage boundary conditions. These column studies generated information regarding the importance of directly connected macropores on pathogen transport to subsurface drains. World Environmental and Water Resources Congress 2008 Ahupua'a © 2008 ASCE Copyright ASCE 2008 World Environmental and Water Resources Congress 2008: Ahupua'a World Environmental and Water Resources Congress 2008 D ow nl oa de d fr om a sc el ib ra ry .o rg b y Io w a St at e U ni ve rs ity o n 03 /0 7/ 17 . C op yr ig ht A SC E . F or p er so na l u se o nl y; a ll ri gh ts r es er ve d.}, booktitle={World Environmental and Water Resources Congress 2008: Ahupua'a - Proceedings of the World Environmental and Water Resources Congress 2008}, author={Fox, G.A. and Kanwar, R. and Guzman, J. and Hoang, C.K. and Malone, R.W. and Moorman, T. and Pederson, C.}, year={2008} }
 @article{fox_kanwar_malone_2008, title={Earthworms and E. coli}, volume={15}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-55649102970&partnerID=MN8TOARS}, number={6}, journal={Resource: Engineering and Technology for Sustainable World}, author={Fox, G.A. and Kanwar, R. and Malone, R.}, year={2008}, pages={22–24} }
 @article{fox_thelin_sabbagh_fuchs_kelly_2008, title={Estimating Watershed Level Nonagricultural Pesticide Use From Golf Courses Using Geospatial Methods}, volume={44}, ISSN={1093-474X 1752-1688}, url={http://dx.doi.org/10.1111/j.1752-1688.2008.00229.x}, DOI={10.1111/j.1752-1688.2008.00229.x}, abstractNote={Abstract:  Limited information exists on pesticide use for nonagricultural purposes, making it difficult to estimate pesticide loadings from nonagricultural sources to surface water and to conduct environmental risk assessments. A method was developed to estimate the amount of pesticide use on recreational turf grasses, specifically golf course turf grasses, for watersheds located throughout the conterminous United States (U.S.). The approach estimates pesticide use: (1) based on the area of recreational turf grasses (used as a surrogate for turf associated with golf courses) within the watershed, which was derived from maps of land cover, and (2) from data on the location and average treatable area of golf courses. The area of golf course turf grasses determined from these two methods was used to calculate the percentage of each watershed planted in golf course turf grass (percent crop area, or PCA). Turf‐grass PCAs derived from the two methods were used with recommended application rates provided on pesticide labels to estimate total pesticide use on recreational turf within 1,606 watersheds associated with surface‐water sources of drinking water. These pesticide use estimates made from label rates and PCAs were compared to use estimates from industry sales data on the amount of each pesticide sold for use within the watershed. The PCAs derived from the land‐cover data had an average value of 0.4% of a watershed with minimum of 0.01% and a maximum of 9.8%, whereas the PCA values that are based on the number of golf courses in a watershed had an average of 0.3% of a watershed with a minimum of <0.01% and a maximum of 14.2%. Both the land‐cover method and the number of golf courses method produced similar PCA distributions, suggesting that either technique may be used to provide a PCA estimate for recreational turf. The average and maximum PCAs generally correlated to watershed size, with the highest PCAs estimated for small watersheds. Using watershed specific PCAs, combined with label rates, resulted in greater than two orders of magnitude over‐estimation of the pesticide use compared to estimates from sales data.}, number={6}, journal={JAWRA Journal of the American Water Resources Association}, publisher={Wiley}, author={Fox, Garey A. and Thelin, Gail P. and Sabbagh, George J. and Fuchs, John W. and Kelly, Iain D.}, year={2008}, month={Dec}, pages={1363–1372} }
 @article{stofleth_shields jr_fox_2008, title={Hyporheic and total transient storage in small, sand-bed streams}, volume={22}, ISSN={0885-6087 1099-1085}, url={http://dx.doi.org/10.1002/hyp.6773}, DOI={10.1002/hyp.6773}, abstractNote={Abstract}, number={12}, journal={Hydrological Processes}, publisher={Wiley}, author={Stofleth, John M. and Shields Jr, F. Douglas and Fox, Garey A.}, year={2008}, pages={1885–1894} }
 @article{cancienne_fox_simon_2008, title={Influence of seepage undercutting on the stability of root-reinforced streambanks}, volume={33}, ISSN={0197-9337 1096-9837}, url={http://dx.doi.org/10.1002/esp.1657}, DOI={10.1002/esp.1657}, abstractNote={Abstract}, number={11}, journal={Earth Surface Processes and Landforms}, publisher={Wiley}, author={Cancienne, Rachel M. and Fox, Garey A. and Simon, Andrew}, year={2008}, month={Oct}, pages={1769–1786} }
 @article{cancienne_fox_2008, title={Laboratory Experiments on Three-Dimensional Seepage Erosion Undercutting of Vegetated Banks}, DOI={10.13031/2013.25035}, abstractNote={Root reinforcement plays a prominent role in streambank stability. Considerable work has analyzed the effects of in situ root reinforcement on soil shear strength. However, the number of controlled studies to quantify root reinforcement with specific instability mechanisms, especially seepage, is limited. Four 50 cm cubic soil blocks, each with a focused inflow reservoir, were constructed to investigate the effects of vegetation on seepage erosion and streambank stability. Experiments included 25-cm tall, 90o loamy sand banks packed at 1.6 g cm-3 bulk densities. A constant head of 25 cm was imposed on the soil to induce flow. Switchgrass (Panicum virgatum) was planted on top of three of the four soil blocks (one as control with bare soil) and was allowed a two-month growth period inside a greenhouse. A laser scanner was utilized to obtain the three-dimensional coordinates of the bank and undercut surfaces at approximately 15 to 30 s intervals. The stressed state of the vegetation yielded lower root reinforcement values (6.2 to 12.4 kPa) than in situ field measurements (i.e. 18 kPa). Soil blocks with greater root reinforcement experienced longer times to bank failure, up to a certain limit, than their counterparts with lower root cohesion values. Separate stability analyses incorporating (1) seepage erosion undercutting and (2) seepage erosion forces confirmed the need for a conglomerate model with both destabilizing mechanisms for streambank stability predictions.}, journal={2008 Providence, Rhode Island, June 29 - July 2, 2008}, publisher={American Society of Agricultural and Biological Engineers}, author={Cancienne, Rachel M and Fox, Garey A}, year={2008} }
 @inproceedings{cancienne_fox_2008, title={Laboratory experiments on three-dimensional seepage erosion undercutting of vegetated banks}, volume={6}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-63049094259&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2008, ASABE 2008}, author={Cancienne, R.M. and Fox, G.A.}, year={2008}, pages={3550–3561} }
 @article{akay_fox_šimůnek_2008, title={Numerical Simulation of Flow Dynamics during Macropore-Subsurface Drain Interactions Using HYDRUS}, volume={7}, ISSN={1539-1663}, url={http://dx.doi.org/10.2136/vzj2007.0148}, DOI={10.2136/vzj2007.0148}, abstractNote={Macropores, such as those created by deep‐burrowing earthworms, have the potential to be hydraulically connected not only to the soil surface but also to subsurface drains. This hydraulic connection may lead to rapid movement of surface‐applied chemicals to receiving waters as they bypass the bulk of the soil matrix. In this study, a numerical model (HYDRUS) that solves the three‐dimensional Richards equation for both matrix and macropore domains was used to analyze previously conducted experiments that contained a single, surface‐connected or buried, artificial macropore and a subsurface drain installed in a laboratory soil column. Both matrix and macropore domains were parameterized using continuous soil hydraulic functions. Simulations confirmed that surface‐connected macropores were highly efficient preferential flow paths that substantially reduced arrival times to the subsurface drainage outlet, with this reduction being directly related to the length of the macropore. Surface‐connected macropores need to extend at least halfway to the drain to have a noticeable effect (>50% reduction) on the arrival time. No significant changes were observed in total drain outflows for columns with laterally shifted macropores (away from a drain) compared with centered macropores unless the macropore depth extended significantly (>75%) into the profile. The model predicted that buried macropores became active and contributed to the total outflow only when pressure heads in the soil profile became positive. The effect of buried macropores on drain flow was investigated for a case where an initially partially saturated profile was drained. Under these conditions, the numerical simulations suggested that buried macropores could contribute up to 40% of the total outflow, which confirms laboratory observations with subsurface‐drained soil columns with macropores.}, number={3}, journal={Vadose Zone Journal}, publisher={Wiley}, author={Akay, Onur and Fox, Garey A. and Šimůnek, Jirka}, year={2008}, month={Aug}, pages={909–918} }
 @article{chu-agor_wilson_fox_2008, title={Numerical modeling of bank instability by seepage erosion undercutting of layered streambanks}, volume={13}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-56449106433&partnerID=MN8TOARS}, DOI={10.1061/(ASCE)1084-0699(2008)13:12(1133)}, abstractNote={Undercutting, primarily considered due to fluvial mechanisms, has been reported to have a major impact on slope failure. Predicting bank collapse specifically due to seepage erosion undercutting by particle mobilization on layered streambanks has not been fully studied or modeled, even though its role in streambank erosion may be important. The limitation originates from the limited field measurements or laboratory experiments as well as the unavailability of discrete element models that can effectively simulate seepage particle mobilization, undercutting, and the corresponding mass wasting. The objective of this research was to demonstrate a procedure for incorporating seepage undercutting into bank stability models and to investigate the role of seepage undercutting on bank instability. The question to be addressed is whether seepage particle mobilization can lead to distances of undercutting that are a significant cause of bank instability. A numerical finite-element model, SEEP/W, was used to model so...}, number={12}, journal={Journal of Hydrologic Engineering}, author={Chu-Agor, M.L. and Wilson, G.V. and Fox, G.A.}, year={2008}, pages={1133–1145} }
 @article{chu-agor_fox_cancienne_wilson_2008, title={Seepage caused tension failures and erosion undercutting of hillslopes}, volume={359}, ISSN={0022-1694}, url={http://dx.doi.org/10.1016/j.jhydrol.2008.07.005}, DOI={10.1016/j.jhydrol.2008.07.005}, abstractNote={Seepage has been suggested as an important factor in gully and river bank erosion. This study investigated the underlying mechanisms of instability by seepage in laboratory studies. A 25-cm tall, 50-cm wide, and 20-cm long soil block with a focused inflow reservoir was constructed to investigate seepage gradient forces and the three-dimensional nature of seepage particle mobilization (i.e., seepage erosion) and undercutting. Experiments included sand and loamy sand soil blocks packed at prescribed bulk densities (1.30–1.70 Mg m−3) and with an outflow face at various angles (90°, 75°, and 60°). Constant heads of 15, 25, and 35 cm were imposed on the soil to induce flow. A laser scanner was utilized to obtain the three-dimensional coordinates of the bank and undercut surfaces at approximately 15–30 s intervals. The bulk density of the two different soil types controlled which seepage failure mechanism occurred: (1) tension or "pop-out" failures due to the seepage force exceeding the soil shear strength which was being concurrently reduced by increased soil pore-water pressure, or (2) particle entrainment in the seepage flow, particle mobilization, bank undercutting, and bank collapse when the initial seepage force gradient was less than the resistance of the soil block. For cases experiencing particle mobilization and undercutting, seepage erosion initiated as unimodal (i.e., concentrated at one point) or as multimodal (i.e., initiating at several locations across the bank face), and this result was largely controlled by the bank angle. A five parameter Gaussian function was fitted to the measured three-dimensional undercut shapes to derive parameters for the maximum depth of undercutting, position of the center of the peak, and the vertical and lateral spreads of the undercut. The parameters of this distribution can be useful in the development of improved sediment transport functions and the incorporation of this failure mechanism into hillslope stability models.}, number={3-4}, journal={Journal of Hydrology}, publisher={Elsevier BV}, author={Chu-Agor, M.L. and Fox, G.A. and Cancienne, R.M. and Wilson, G.V.}, year={2008}, month={Sep}, pages={247–259} }
 @inproceedings{fox_chu-agor_cancienne_wilson_2008, title={Seepage erosion mechanisms of bank collapse: Three-dimensional seepage particle mobilization and undercutting}, volume={316}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79251522194&partnerID=MN8TOARS}, DOI={10.1061/40976(316)292}, abstractNote={Seepage flow initiates undercutting, similar to development and headward migration of internal gullies, by liquefaction of soil particles, followed by mass wasting of the bank. Although seepage erosion has three-dimensional characteristics, two-dimensional lysimeters have been used in previous research to analyze for the hydraulic and geotechnical controls on this mechanism of hillslope, gully, and bank instability. A 50 cm cubic soil block with a focused inflow reservoir was constructed to investigate the mechanisms of seepage erosion and the three-dimensional nature of seepage undercutting. Experiments included 25-cm tall, sand and loamy sand soil blocks packed at prescribed bulk densities (1.30 to 1.70 g cm–3) and with an outflow face at various angles (90, 75, and 60 degrees). Constant heads of 15 cm, 25 cm, and 35 cm were imposed on the soil to induce flow. A laser scanner was utilized to obtain the three-dimensional coordinates of the bank and undercut surfaces at 15 to 30 s intervals. The bulk density for the two different soil types controlled which seepage failure mechanism occurred: (1) tension or "pop-out" failures due to the seepage force exceeding the soil shear strength, or (2) particle entrainment in the seepage flow, particle mobilization, bank undercutting, and bank collapse when the seepage force gradient was initially less than the initial resistance force of the soil block. For cases experiencing particle mobilization and undercutting, seepage erosion initiated as unimodal (i.e., concentrated at one point) or as multimodal (i.e., initiating at several locations across the bank face), largely controlled by the bank angle. As a first approximation, a three-dimensional, five-parameter Gaussian distribution was fit to the undercut shapes to derive parameters for the maximum depth of undercutting, position of the center of the peak, and the vertical and lateral spreads of the undercut.}, booktitle={World Environmental and Water Resources Congress 2008: Ahupua'a - Proceedings of the World Environmental and Water Resources Congress 2008}, author={Fox, G.A. and Chu-Agor, M.L. and Cancienne, R.M. and Wilson, G.V.}, year={2008} }
 @article{chu-agor_cancienne_fox_wilson_2008, title={Slope Failure Mechanisms due to Seepage: Three-Dimensional Soil Block Experiments}, DOI={10.13031/2013.24952}, abstractNote={Seepage erosion has been suggested to potentially play an important role in streambank failure and gully formation. However, although seepage erosion has three-dimensional characteristics, two-dimensional lysimeters were used in previous research to analyze for the hydraulic and geotechnical controls on this mechanism of instability. In this research, a three-dimensional soil block (50 cm by 50 cm by 50 cm with an inflow reservoir capable of generating water heads of 50 cm) was constructed to investigate the three-dimensional nature of seepage undercutting and to derive an improved sediment transport function. Two different soil types (sand and loamy sand) were utilized in these three-dimensional experiments with varying water inflow reservoir heads (15 cm, 25 cm, and 35 cm). Each soil type was packed at various bulk densities (1300, 1450 and 1600 kg/m3 for the sand and 1300, 1450, 1600 and 1700 kg/m3 for the loamy sand) to create a 25 cm tall bank. The bottom of the soil block was lined with densely packed clay to a height of 2.5 cm to serve as a restrictive layer and the rest of the block was packed with soil to the desired bulk density in 2.5 cm lifts. The soil was then cut to simulate various bank angles (90o, 75o, and 60o) such that the horizontal centerline for each bank remained 20 cm away from the water inlet. As water flowed through the column, a three-dimensional laser scanner was utilized to obtain the volume of the eroded bank at approximately 15 to 30 s intervals.The hydraulic conditions producing different seepage failure mechanisms were evaluated and the three-dimensional nature of seepage erosion was investigated. Information from these three-dimensional experiments can be used in a stability model for incorporating seepage undercutting as a failure mechanism.}, journal={2008 Providence, Rhode Island, June 29 - July 2, 2008}, publisher={American Society of Agricultural and Biological Engineers}, author={Chu-Agor, Maria and Cancienne, Rachel M and Fox, Garey A and Wilson, Glenn V}, year={2008} }
 @inproceedings{chu-agor_cancienne_fox_wilson_2008, title={Slope Failure Mechanisms due to Seepage: Three-Dimensional Soil Block Experiments}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-63049120190&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2008, ASABE 2008}, author={Chu-Agor, M.L. and Cancienne, R.M. and Fox, G.A. and Wilson, G.}, year={2008}, pages={1701–1713} }
 @article{fuchs_fox_storm_penn_brown_2008, title={Subsurface Transport of Phosphorus in Riparian Floodplains: Tracer and Phosphorus Transport Experiments}, DOI={10.13031/2013.24706}, abstractNote={The primary transport mechanism for phosphorus (P) movement from upland areas to surface water systems is typically surface runoff, with subsurface transport assumed negligible. However, certain local conditions can lead to an environment where subsurface transport may be significant. The objective of this research was to determine the importance of subsurface transport of P along streams characterized by cherty or gravel subsoils. At a field site adjacent to the Barren Fork Creek, a trench was installed with the bottom of the trench at the topsoil/alluvial gravel interface. Fifteen piezometers were installed at various locations surrounding the trench in order to monitor flow and transport. In three separate experiments, water was pumped into the trench from the Barren Fork Creek to maintain a constant head. At the same time, a conservative tracer (Rhodamine WT) and/or potassium phosphate were injected into the trench at concentrations ranging between 3 and 100 ppm for Rhodamine WT and at 100 ppm for P. Rhodamine WT and P were detected in some piezometers at equivalent concentrations as measured in the trench, suggesting the presence of preferential flow pathways. Phosphorus sorption was minimal along the preferential flow pathways but transport was retarded in non-preferential flow paths.}, journal={2008 Providence, Rhode Island, June 29 - July 2, 2008}, publisher={American Society of Agricultural and Biological Engineers}, author={Fuchs, John William and Fox, Garey A and Storm, Dan and Penn, Chad and Brown, Glenn O}, year={2008} }
 @inproceedings{fuchs_fox_storm_penn_brown_2008, title={Subsurface transport of phosphorus in riparian floodplains: Tracer and phosphorus transport experiments}, volume={9}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-63049103369&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2008, ASABE 2008}, author={Fuchs, J.W. and Fox, G. and Storm, D. and Penn, C. and Brown, G.}, year={2008}, pages={5741–5752} }
 @inproceedings{fox_2008, title={Surface water and groundwater interactions: Investigating the connections}, booktitle={Centennial Session on Advances in Soil and Water Engineering}, author={Fox, G.A.}, editor={Skaggs, R.W.Editor}, year={2008} }
 @article{guzmán_fox_2008, title={The Role of Drainage System and Macropore Interconnectivity in Soil Pathogen Transport}, DOI={10.13031/2013.24951}, abstractNote={The primary transport of pathogenic microorganisms in soils occurs through macropores that bypass the filtering and adsorptive effects of the soil. Recent research indicates immediate breakthrough of solutes and contaminants in subsurface drainage by extraordinarily efficient transport through directly connected macropores. In this study, an innovative soil column packed with loamy sand soil was used to simulate the transport of E. coli through directly connected macropore into the subsurface drainage systems. Four experiments simulating open surface connected and buried macropores were performed. The soil column was flushed with distilled water, diluted swine manure, and finally with distilled water at 0, 48, and 96 hours, respectively, after packing. Both open surface connected and buried macropores were capable of transporting E. coli to the subsurface drain. During the manure flushing, breakthrough time in both discharge and E. coli was inversely proportional to the macropore length. In the macropore, E. coli detection occurred simultaneously with macropore discharge breakthrough. For open surface connected macropores that extended the entire distance between the soil surface and drain except for the last 10 to 20 cm, the maximum E. coli concentrations in the drain flow was approximately 20 to 30% of the inflow E. coli concentration. For buried macropores, maximum E. coli concentrations in the drain flow were approximately 10% of the initial concentration but 25 to 40% in the macropore. The highest E. coli recovery concentrations occurred during the final distilled water flush, approximately 48 hours after manure application. It was hypothesized that these peak concentrations were due to the development of an E. coli pool within the capillary fringe. The findings of this study stress the importance of directly connected macropores to subsurface drainage systems in allowing E. coli to bypass the soil filter capacity, especially after rainfall events or irrigation following manure application.}, journal={2008 Providence, Rhode Island, June 29 - July 2, 2008}, publisher={American Society of Agricultural and Biological Engineers}, author={Guzmán, Jorge A and Fox, Garey A}, year={2008} }
 @inproceedings{guzmán_fox_2008, title={The role of drainage system and macropore interconnectivity in soil pathogen transport}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-63049133110&partnerID=MN8TOARS}, booktitle={American Society of Agricultural and Biological Engineers Annual International Meeting 2008, ASABE 2008}, author={Guzmán, J.A. and Fox, G.}, year={2008}, pages={1689–1700} }
 @article{mittelstet_smolen_fox_2008, title={Using MODFLOW to Compare Management Alternatives for a River Alluvial Aquifer}, DOI={10.13031/2013.27228}, abstractNote={The ground water policies of Oklahoma and the Texas Panhandle Groundwater Conservation District (GCD) were compared to determine their effects on sustainability of an alluvial aquifer. The Oklahoma policy permits each well to withdraw water at a rate projected to allow not more than 50% of wells to go dry in 20 years. The GCD policy permits pumping at a rate that will consume no more than 50% of the water in 50 years, with reevaluation and readjustment of permits every five years. MODFLOW (Harbaugh and McDonald, 1996) simulations showed that at low development, Oklahoma's policy will limit the pumping rate more than the GCD policy. As development exceeds 65% of the area, more than half of aquifer storage will be depleted. The reevaluation required by the GCD policy will not permit aquifer storage to decline below 50%. Both Oklahoma and GCD policy will reduce baseflow of the river when development exceeds approximately 10%.}, journal={2009 Reno, Nevada, June 21 - June 24, 2009}, publisher={American Society of Agricultural and Biological Engineers}, author={Mittelstet, Aaron R and Smolen, Michael D and Fox, Garey A}, year={2008} }
 @article{fox_akay_malone_ma_sabbagh_2007, title={An Improved Express Fraction for Modeling Macropore/Subsurface Drain Interconnectivity}, DOI={10.13031/2013.23235}, abstractNote={The rapid transport of contaminants through macropores and into subsurface drains is a concern. Recent research has proposed methods for incorporating this direct connectivity into contaminant transport models. For example, the one-dimensional pesticide fate and transport model, Root Zone Water Quality Model (RZWQM), was modified to include an express fraction parameter based on the percentage of macropores in direct hydraulic connection to subsurface drains. When macropore flow first reached the top of the water table (point midway between the drains), a macropore express fraction of water and chemical was routed directly into the subsurface drain, which improved predictions of concentration peaks. The remaining water and chemical was allowed to fill and mix with the water table, resulting in a concentration bulge at the water table. This research proposes an updated express fraction for RZWQM, which distributes water across all saturated layers between the drain and water table. Implicitly assumed is a uniform spatial distribution of macropores. This updated express fraction is evaluated using data from two isoxaflutole/metabolite field experiments in Allen County and Owen County IN (2000), where concentrations of parent and metabolite were measured in the drain flow. The results showed a slight improvement in the prediction of chemical concentrations on the recession limbs of drainage hydrographs.}, journal={2007 Minneapolis, Minnesota, June 17-20, 2007}, publisher={American Society of Agricultural and Biological Engineers}, author={Fox, Garey A and Akay, Onur and Malone, Rob W and Ma, Liwang and Sabbagh, George J}, year={2007} }
 @inproceedings{fox_akay_malone_ma_sabbagh_2007, title={An improved express fraction for modeling macropore/subsurface drain interconnectivity}, volume={4 BOOK}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-35648947771&partnerID=MN8TOARS}, booktitle={2007 ASABE Annual International Meeting, Technical Papers}, author={Fox, G.A. and Akay, O. and Malone, R. and Ma, L. and Sabbagh, G.}, year={2007} }
 @article{fox_fuchs_medina_atapattu_2007, title={Capture of airborne particulate using surface applied emulsions: Potential for postdetonation dirty bomb cleanup}, volume={133}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33847204998&partnerID=MN8TOARS}, DOI={10.1061/(ASCE)0733-9372(2007)133:3(255)}, abstractNote={Recent research has proposed the use of asphalt and tall-oil-pitch emulsions for stabilizing radioactive contamination deposited on surfaces in urban areas. The objective of this project was to investigate whether surface applied emulsions could capture airborne radioactive particulate. Laboratory experiments included wind-blown particulate capture studies using an acrylic column and particulate retainment experiments using a wind box capable of producing wind speeds of 96 km∕h . A probe methodology was developed to relate particulate retainment to a tack force on the emulsion surface. Experiments were also performed to determine the potential for such emulsions to absorb particulate matter into their emulsion matrix. Tall-oil-pitch emulsions outperformed asphalt emulsions in terms of particulate retention, tack force, and the ability to absorb magnesium silicate. Both tall-oil-pitch and asphalt emulsions were capable of extracting 22–24 g m−2 of powder from particulate-laden airflow. Tall-oil-pitch emuls...}, number={3}, journal={Journal of Environmental Engineering}, author={Fox, G.A. and Fuchs, J.W. and Medina, V.F. and Atapattu, K.}, year={2007}, pages={255–262} }
 @article{fox_gordji_2007, title={Consideration for unsaturated flow beneath a streambed during alluvial well depletion}, volume={12}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33847177625&partnerID=MN8TOARS}, DOI={10.1061/(ASCE)1084-0699(2007)12:2(139)}, abstractNote={Unsaturated flow transforms streams from constant head boundaries to constant flux boundaries, impacting the quantity of stream recharge to groundwater. The objective of this research was to analyze the impact of unsaturated flow on stream/aquifer exchange by incorporating a three-regime, saturated/unsaturated flow, stream recharge model into MODFLOW, the most commonly used numerical flow model in ground water hydrology. This three-regime model extends prior research by accounting for a transition regime between fully saturated and gravity-driven unsaturated flow. Accounting for unsaturated flow between a stream and aquifer is necessary to adequately simulate stream depletion. Sensitivity analyses of steady stream recharge versus drawdown demonstrated that the transition regime became more important for cases with small stream stages, smaller streambed thicknesses, and larger entry pressure heads. Based on coarse sand and fine sand hypothetical scenarios, the transition regime in the proposed three-regime model could generally be neglected with minor error for most stream/aquifer scenarios. However, the transition regime became important when: (1) the drawdown stabilized near the range of drawdowns that represented the transition regime; and (2) there must be a significant difference (i.e., 0.2 m) in the entry and ultimate capillary pressure heads, which occurred with larger entry pressure heads (i.e., equal to or greater than 1.0 m) and a smaller pore size distribution index (i.e., approximately 1.0).}, number={2}, journal={Journal of Hydrologic Engineering}, author={Fox, G.A. and Gordji, L.}, year={2007}, pages={139–145} }
 @article{fox_chu-agor_wilson_2007, title={Erosion of Noncohesive Sediment by Groundwater Seepage: Lysimeter Experiments and Modeling}, DOI={10.13031/2013.23422}, abstractNote={Seepage may be a significant mechanism of streambank erosion and failure in numerous geographical locations. Previous research has investigated erosion by lateral subsurface flow and developed a sediment transport model similar to an excess shear stress equation. As a continuation of this earlier research, slope destabilization driven by lateral, subsurface flow was studied to further verify the recently proposed sediment transport model. Laboratory experiments were performed using a two-dimensional soil lysimeter. The experiments were conducted on two sandy soils: a field soil (loamy sand) and a sieved sand with greater sand content and less cohesion. A series of seven lysimeter experiments were performed for the two different sands by varying the bank slope (90o, 60o, 45o, 36o, and 26o). Flow and sediment concentrations were measured at the outflow flume. Pencil-size tensiometers were used to measure soil pore-water pressure. Results indicate that a slight modification of the existing seepage sediment transport model adequately simulates lysimeter experiments for both noncohesive soils without modifying the seepage parameters of the excess shear stress equation, especially for bank angles greater than 45o. The research then determined whether integrated finite element and bank stability models were capable of capturing both small and large scale sapping failures. The models predicted large-scale failures for bank angles greater than 45o in which tension cracks formed on the bank surface. The models failed to predict collapses for bank angles less than 45o in which tension cracks formed on the seepage face. The failure to predict collapse was hypothesized to be due to the assumption of circular arc slip surfaces.}, journal={2007 Minneapolis, Minnesota, June 17-20, 2007}, publisher={American Society of Agricultural and Biological Engineers}, author={Fox, Garey A and Chu-Agor, Maria and Wilson, Glenn V}, year={2007} }
 @article{fox_chu-agor_wilson_2007, title={Erosion of noncohesive sediment by ground water seepage: Lysimeter experiments and stability modeling}, volume={71}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-36448981038&partnerID=MN8TOARS}, DOI={10.2136/sssaj2007.0090}, abstractNote={Seepage may be a significant mechanism of streambank erosion and failure in numerous geographical locations. Previous research investigated erosion by lateral subsurface flow and developed a sediment transport model similar to an excess shear stress equation. As a continuation of this earlier research, slope destabilization driven by lateral, subsurface flow was studied to further verify the recently proposed sediment transport model. Laboratory experiments were performed using a two‐dimensional soil lysimeter. The experiments were conducted on two sandy soils: a field soil (loamy sand) and sieved sand with greater sand content and less cohesion. A series of seven lysimeter experiments were performed for the two different sands by varying the bank slope (90, 60, 45, 36, and 26°). Flow and sediment concentrations were measured at the outflow flume. Pencil‐size tensiometers were used to measure soil pore‐water pressure. A slight modification of the existing seepage sediment transport model adequately simulated lysimeter experiments for both noncohesive soils without modifying the seepage parameters of the excess shear stress equation, especially for bank angles >45°. The research then determined whether integrated finite element and bank stability models were capable of capturing both small‐ and large‐scale sapping failures. The models predicted large‐scale failures for bank angles >45° in which tension cracks formed on the bank surface. The models failed to predict collapses for bank angles <45° in which tension cracks formed on the seepage face. The failure to predict collapse was hypothesized to be due to the assumption of circular arc slip surfaces. More analytically complex stability approaches are needed to capture bank slope undermining.}, number={6}, journal={Soil Science Society of America Journal}, author={Fox, G.A. and Chu-Agor, Ma.L. and Wilson, G.V.}, year={2007}, pages={1822–1830} }
 @inproceedings{fox_chu-agor_wilson_2007, title={Erosion of noncohesive sediment by groundwater seepage: Lysimeter experiments and modeling}, volume={5 BOOK}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-35648961784&partnerID=MN8TOARS}, booktitle={2007 ASABE Annual International Meeting, Technical Papers}, author={Fox, G.A. and Chu-Agor, M. and Wilson, G.}, year={2007} }
 @article{fox_2007, title={Estimating streambed conductivity: Guidelines for stream-aquifer analysis tests}, volume={50}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33947717890&partnerID=MN8TOARS}, number={1}, journal={Transactions of the ASABE}, author={Fox, G.A.}, year={2007}, pages={107–113} }
 @article{akay_fox_2007, title={Experimental investigation of direct connectivity between macropores and subsurface drains during infiltration}, volume={71}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-35649011237&partnerID=MN8TOARS}, DOI={10.2136/sssaj2006.0359}, abstractNote={Recent research indicates immediate breakthrough of surface‐applied contaminants in subsurface drainage by transport through macropores directly connected to the surface. This “direct connectivity” phenomenon was verified and investigated by conducting infiltration experiments (1‐cm ponded water at the soil surface) in a laboratory soil column (sandy loam soil with bulk density of 1.6 g cm−3) with a vertical artificial macropore placed directly above or shifted away from a lateral subsurface drain. The experimental setup allowed surface‐connected and buried macropore lengths to be varied from the surface to the subsurface drain depth without unpacking or disturbing the soil column between experiments. It was observed that the longer the buried macropore length (i.e., as the macropore approached the soil surface), the more rapid the response at the drain outlet in addition to an increased percentage of total drain flow through the macropore (35–40%). Breakthrough with surface‐connected macropores was significantly faster than with buried macropores, suggesting that breaking surface connectivity of macropores by tillage may be an important management strategy. For surface‐connected macropore experiments, the average ratio of steady‐state total (macropore and matrix) to matrix flow rates decreased as the distance from the drain increased: 2.4, 2.1, and 1.6 for distances of 0, 6.25, and 12.5 cm, respectively. Extrapolating this data to distances beyond 12.5 cm suggested that macropores located within 20 to 25 cm of the drain act as though directly connected in this sandy loam soil. This research verifies the “contributing area” concept hypothesized in previous field and numerical modeling studies.}, number={5}, journal={Soil Science Society of America Journal}, author={Akay, O. and Fox, G.A.}, year={2007}, pages={1600–1606} }
 @inproceedings{akay_fox_2007, title={Experimental investigation of direct connectivity between macropores and subsurface drains during infiltration}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84855161198&partnerID=MN8TOARS}, DOI={10.1061/40856(200)301}, abstractNote={Laboratory experiments are commonly utilized for investigating the effect of macropore flow on contaminant transport. Most research to date has focused on lateral water and solute diffusion between macropores and the soil matrix with controlled bottom flux or specified pressure head boundary conditions as opposed to simulating local drainage flux to tile drains. Furthermore, recent research indicates immediate breakthrough of solutes and pesticides in subsurface drainage by extraordinarily efficient transport through directly connected macropores. Macropores, such as those created by earthworm burrows, have been documented to transfer water and solutes directly to subsurface drains. In this study, this "direct connectivity" phenomenon was verified by conducting infiltration experiments in a laboratory column (28 cm by 50 cm rectangular cross-section with length of 95 cm) with an artificial macropore directly connected to the subsurface drain. A novel design of the experimental setup allowed open surface and buried macropore lengths to be varied from the subsurface drain to the surface without unpacking/disturbing the soil column between experiments. Experiments were completed for various buried macropore lengths ranging from zero (no macropore effect) to 75 cm (surface connected macropore). The column was packed with a sandy loam soil with bulk density of 1.6 g/cm3. For each experiment, a 1-cm ponded boundary condition was maintained at the soil surface. Breakthrough curves were plotted for both matrix and macropore flow at the outlet. The movement of the wave front down the column was observed with pencil size tensiometers mounted on the side of the column at various depths. The macropore and soil matrix outflow revealed hydraulic nonequilibrium between soil matrix and macropore domains. It was observed that the longer the buried macropore length (i.e., as the macropore approached the soil surface), the more rapid response occurred at the drain outlet in addition to an increased percentage of total drain flow through the macropore. Breakthrough times with the surface connected macropore decreased significantly compared to buried macropores. This research also suggests that "drain connected" macropores may not necessarily have to possess a direct physical connection to subsurface drainage.}, booktitle={Examining the Confluence of Environmental and Water Concerns - Proceedings of the World Environmental and Water Resources Congress 2006}, author={Akay, O. and Fox, G.A.}, year={2007} }
 @article{fox_pulijala_sabbagh_2007, title={Influence of Rainfall Distribution on Simulations of Atrazine, Metolachlor, and Isoxaflutole/Metabolite Transport in Subsurface Drained Fields}, volume={55}, ISSN={0021-8561 1520-5118}, url={http://dx.doi.org/10.1021/jf063753z}, DOI={10.1021/jf063753z}, abstractNote={This research investigated the impact of modeling atrazine, metolachlor, and isoxaflutole/metabolite transport in artificially subsurface drained sites with temporally discrete rainfall data. Differences in considering rainfall distribution are unknown in regard to estimating agrochemical fluxes in the subsurface. The Root Zone Water Quality Model (RZWQM) simulated pesticide fate and transport at three subsurface drained sites: metolachlor/atrazine field experiment in Baton Rouge, LA (1987), and two isoxaflutole/metabolite field experiments in Allen County and Owen County, Indiana (2000). The modeling assumed linear, equilibrium sorption based on average reported physicochemical and environmental fate properties. Assumed rainfall intensity and duration influenced transport by runoff more than transport by subsurface drainage. As the importance of macropore flow increased, the necessity for using temporally discrete rainfall data became more critical. Long-term simulations indicated no significant difference between average or upper percentile (i.e., <2% difference in percent loss as a function of mass applied) atrazine, metolachlor, or isoxaflutole/metabolite loss through subsurface drainage among the three different rainfall assumptions. It was necessary (i.e., within 7% of predicted loss) to use hourly or average duration storm events as opposed to daily rainfall data for total (i.e., runoff and subsurface drainage) pesticide loss over the long term.}, number={14}, journal={Journal of Agricultural and Food Chemistry}, publisher={American Chemical Society (ACS)}, author={Fox, Garey A. and Pulijala, Sri H. and Sabbagh, George J.}, year={2007}, month={Jul}, pages={5399–5407} }
 @article{fox_wilson_simon_langendoen_akay_fuchs_2007, title={Measuring streambank erosion due to ground water seepage: correlation to bank pore water pressure, precipitation and stream stage}, volume={32}, url={http://dx.doi.org/10.1002/esp.1490}, DOI={10.1002/esp.1490}, abstractNote={Abstract}, number={10}, journal={Earth Surface Processes and Landforms}, author={Fox, G.A. and Wilson, G.V. and Simon, A. and Langendoen, E.J. and Akay, O. and Fuchs, J.W.}, year={2007}, month={Sep}, pages={1558–1573} }
 @article{fox_sabbagh_malone_rojas_2007, title={Modeling parent and metabolite fate and transport in subsurface drained fields with directly connected macropores}, volume={43}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-35648974021&partnerID=MN8TOARS}, DOI={10.1111/j.1752-1688.2007.00116.x}, abstractNote={Abstract:  Few studies exist that evaluate or apply pesticide transport models based on measured parent and metabolite concentrations in fields with subsurface drainage. Furthermore, recent research suggests pesticide transport through exceedingly efficient direct connections, which occur when macropores are hydrologically connected to subsurface drains, but this connectivity has been simulated at only one field site in Allen County, Indiana. This research evaluates the Root Zone Water Quality Model (RZWQM) in simulating the transport of a parent compound and its metabolite at two subsurface drained field sites. Previous research used one of the field sites to test the original modification of the RZWQM to simulate directly connected macropores for bromide and the parent compound, but not for the metabolite. This research will evaluate RZWQM for parent/metabolite transformation and transport at this first field site, along with evaluating the model at an additional field site to evaluate whether the parameters for direct connectivity are transferable and whether model performance is consistent for the two field sites with unique soil, hydrologic, and environmental conditions. Isoxaflutole, the active ingredient in BALANCE® herbicide, was applied to both fields. Isoxaflutole rapidly degrades into a metabolite (RPA 202248). This research used calibrated RZWQM models for each field based on observed subsurface drain flow and/or edge of field conservative tracer concentrations in subsurface flow. The calibrated models for both field sites required a portion (approximately 2% but this fraction may require calibration) of the available water and chemical in macropore flow to be routed directly into the subsurface drains to simulate peak concentrations in edge of field subsurface drain flow shortly after chemical applications. Confirming the results from the first field site, the existing modification for directly connected macropores continually failed to predict pesticide concentrations on the recession limbs of drainage hydrographs, suggesting that the current strategy only partially accounts for direct connectivity. Thirty‐year distributions of annual mass (drainage) loss of parent and metabolite in terms of percent of isoxaflutole applied suggested annual simulated percent losses of parent and metabolite (3.04 and 1.31%) no greater in drainage than losses in runoff on nondrained fields as reported in the literature.}, number={6}, journal={Journal of the American Water Resources Association}, author={Fox, G.A. and Sabbagh, G.J. and Malone, R.W. and Rojas, K.}, year={2007}, pages={1359–1372} }
 @article{sabbagh_fox_ma_malone_arthur_dyer_2007, title={Modeling pesticide fate and nonideal transport from seeds treated with a slow-release pesticide in a laboratory soil column}, volume={50}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34347229430&partnerID=MN8TOARS}, number={2}, journal={Transactions of the ASABE}, author={Sabbagh, G.J. and Fox, G.A. and Ma, L. and Malone, R.W. and Arthur, E.L. and Dyer, D.G.}, year={2007}, pages={523–532} }
 @inproceedings{chu-agor_wilson_fox_2007, title={Modeling streambank instability by seepage undercutting}, volume={4 BOOK}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-35649019650&partnerID=MN8TOARS}, booktitle={2007 ASABE Annual International Meeting, Technical Papers}, author={Chu-Agor, M.L. and Wilson, G. and Fox, G.A.}, year={2007} }
 @inproceedings{chu-agor_wilson_fox_2007, place={St. Joseph, Michigan}, title={Numerical modeling of bank instability by groundwater seepage flow}, DOI={10.13031/2013.23228}, abstractNote={Predicting bank collapse due to seepage erosion undercutting has not been fully studied or modeled, even though its role in streambank erosion may be important. The limitation originates from the lack of field measurements or laboratory experiments as well as the unavailability of discrete element models that can effectively simulate seepage erosion. The objective of this research was to demonstrate a procedure for incorporating seepage undercutting into two-dimensional variably-saturated flow and bank stability models and to investigate the role of seepage undercutting on bank instability. Integrated flow and bank stability models were used to simulate soil-water pressure variations and bank stability with and without seepage erosion with regard to input parameter uncertainty using Monte Carlo analysis. The percentage decrease in the mean factor of safety, Fs, ranged between 42 and 91% as the depth of undercutting increased, dependent upon the initial stability of the bank. For stable banks, the probability of failure reached 100% when the depth of the undercutting reached 30 to 50 mm. The propensity of streambanks to fail during the recession limb of hydrographs may be the combined result of seepage undercutting and reduced cohesion.}, number={072117072117}, booktitle={2007 Minneapolis, Minnesota, June 17-20, 2007}, publisher={American Society of Agricultural and Biological Engineers}, author={Chu-Agor, M.L. and Wilson, G.V. and Fox, G.A.}, year={2007} }
 @inproceedings{fox_chu-agor_wilson_2007, title={Seepage Erosion: A Significant Mechanism of Stream Bank Failure}, ISBN={9780784409275}, url={http://dx.doi.org/10.1061/40927(243)350}, DOI={10.1061/40927(243)350}, abstractNote={The role of seepage undercutting on mass failure of stream banks is not well defined relative to other streambank failure mechanisms. Seepage flow initiates undercutting, similar to development and headward migration of internal gullies, by liquefaction of soil particles, followed by mass wasting of the stream bank. The objectives of this research were to quantify the impact of seepage undercutting on streambank stability based upon seepage flow and erosion measurements from two deeply incised streams in northern Mississippi: Little Topashaw Creek (LTC) and Goodwin Creek (GC). Stream bank soil properties characterized from disturbed and undisturbed soil cores suggested that the type of seepage erosion (seepage erosion of a conductive layer and undercutting of layers underneath the seepage layer) at LTC and GC was a function of the bank stratigraphy. At LTC, seepage eroded sediment from the conductive, relatively noncohesive loamy sand layer. The GC seeps originated from the conductive concretion layer, but the flow eroded a less cohesive loamy sand layer below the seepage layer. Subsurface flow and sediment concentrations commonly exceeded 0.1 m3 d–1 and 10 g L–1, respectively, as quantified using collection flumes installed into the stream banks. A bank stability model, SLOPE/W, was used to simulate the bank profiles of both LTC and GC based on field measured streambank stratigraphy, soil hydraulic properties and soil strength parameters. Model simulations included numerous bank angles, ground water table elevations, and distances of seepage undercutting. SLOPE/W simulations suggested a 200-mm critical distance of seepage undercutting at which the error in neglecting seepage undercutting became greater than the error in neglecting soil-water pressure effects.}, booktitle={World Environmental and Water Resources Congress 2007}, publisher={American Society of Civil Engineers}, author={Fox, G. A. and Chu-Agor, M. L. and Wilson, G. V.}, year={2007}, month={May} }
 @article{wilson_periketi_fox_dabney_shields_cullum_2007, title={Soil properties controlling seepage erosion contributions to streambank failure}, volume={32}, url={http://dx.doi.org/10.1002/esp.1405}, DOI={10.1002/esp.1405}, abstractNote={Abstract}, number={3}, journal={Earth Surface Processes and Landforms}, author={Wilson, G.V. and Periketi, R.K. and Fox, G.A. and Dabney, S.M. and Shields, F.D. and Cullum, R.F.}, year={2007}, month={Mar}, pages={447–459} }
 @article{caviness_fox_deliman_2006, title={Modeling the big black river: A comparison of water quality models}, volume={42}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33845264827&partnerID=MN8TOARS}, DOI={10.1111/j.1752-1688.2006.tb04480.x}, abstractNote={ABSTRACT:  The Mississippi Department of Environmental Quality uses the Steady Riverine Environmental Assessment Model (STREAM) to establish effluent limitations. While the U.S. Environmental Protection Agency has approved of its use, questions arise regarding the model's simplicity. The objective of this research was to compare STREAM with the more commonly utilized Enhanced Stream Water Quality Model (QUAL2E). The comparison involved a statistical evaluation procedure based on sensitivity analyses, input probability distribution functions, and Monte Carlo simulation with site‐specific data from a 46‐mile (74‐km) reach of the Big Black River in central Mississippi. Site specific probability distribution functions were derived from measured rates of reaeration, sediment oxygen demand, photosynthesis, and respiration. Both STREAM and QUAL2E reasonably predicted daily average dissolved oxygen (DO) based on a comparison of output probability distributions with observed DO. Observed DO was consistently within 90 percent confidence intervals of model predictions. The STREAM approach generally overpredicted while QUAL2E generally matched observed DO. Using the more commonly assumed lognormal distribution as opposed to a Weibull distribution for two of the sensitive input parameters resulted in minimal differences in the statistical evaluations. The QUAL2E approach had distinct advantages over STREAM in simulating the growth cycle of algae.}, number={3}, journal={Journal of the American Water Resources Association}, author={Caviness, K.S. and Fox, G.A. and Deliman, P.N.}, year={2006}, pages={617–627} }
 @article{fox_wilson_periketi_cullum_2006, title={Sediment transport model for seepage erosion of streambank sediment}, volume={11}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33750106153&partnerID=MN8TOARS}, DOI={10.1061/(ASCE)1084-0699(2006)11:6(603)}, abstractNote={Erosion by lateral, subsurface flow is known to erode streambank sediment in numerous geographical locations; however, the role of seepage erosion on mass failure of streambanks is not well understood. In the absence of an established sediment transport model for seepage erosion, the objectives of this research were to investigate the mechanisms of erosion due to concentrated, lateral subsurface flow and develop an empirical sediment transport model for seepage erosion of noncohesive sediment on near-vertical streambanks. Laboratory experiments were performed using a two-dimensional soil lysimeter of a reconstructed streambank profile packed with three different soil layers to mimic seepage erosion occurring at Little Topashaw Creek (LTC) in northern Mississippi. Soil samples from LTC streambanks indicated considerable hydraulic conductivity contrast between an overlying silt loam layer (SiL), highly permeable loamy sand, and confining clay loam layer. Lysimeter experiments were conducted with various ups...}, number={6}, journal={Journal of Hydrologic Engineering}, author={Fox, G.A. and Wilson, G.V. and Periketi, R.K. and Cullum, R.F.}, year={2006}, pages={603–611} }
 @article{fox_sabbagh_chen_russell_2006, title={Uncalibrated modelling of conservative tracer and pesticide leaching to groundwater: Comparison of potential Tier II exposure assessment models}, volume={62}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33744947346&partnerID=MN8TOARS}, DOI={10.1002/ps.1211}, abstractNote={Abstract}, number={6}, journal={Pest Management Science}, author={Fox, G.A. and Sabbagh, G.J. and Chen, W. and Russell, M.H.}, year={2006}, pages={537–550} }
 @inproceedings{fox_wilson_periketi_cullum_2005, title={Developing a sediment transport model for the seepage erosion of streambank sediment}, booktitle={Proceedings of the American Water Resources Conference}, author={Fox, G.A. and Wilson, G.V. and Periketi, R. and Cullum, R.F.}, year={2005} }
 @article{fox_medina_2005, title={Evaluating factors affecting the permeability of emulsions used to stabilize radioactive contamination from a radiological dispersal device}, volume={39}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-18944402594&partnerID=MN8TOARS}, DOI={10.1021/es048710i}, abstractNote={Present strategies for alleviating radioactive contamination from a radiological dispersal device (RDD) or dirty bomb involve either demolishing and removing radioactive surfaces or abandoning portions of the area near the release point. In both cases, it is imperative to eliminate or reduce migration of the radioisotopes until the cleanup is complete or until the radiation has decayed back to acceptable levels. This research investigated an alternative strategy of using emulsions to stabilize radioactive particulate contamination. Emergency response personnel would coat surfaces with emulsions consisting of asphalt or tall oil pitch to prevent migration of contamination. The site can then be evaluated and cleaned up as needed. In order for this approach to be effective, the treatment must eliminate migration of the radioactive agents in the terror device. Water application is an environmental condition that could promote migration into the external environment. This research investigated the potential for water, and correspondingly contaminant, migration through two emulsions consisting of Topein, a resinous byproduct during paper manufacture. Topein C is an asphaltic-based emulsion and Topein S is a tall oil pitch, nonionic emulsion. Experiments included water adsorption/ mobilization studies, filtration tests, and image analysis of photomicrographs from an environmental scanning electron microscope (ESEM) and a stereomicroscope. Both emulsions were effective at reducing water migration. Conductivity estimates were on the order of 10(-80) cm s(-1) for Topein C and 10(-7) cm s(-1) for Topein S. Water mobility depended on emulsion flocculation and coalescence time. Photomicrographs indicate that Topein S consisted of greater and more interconnected porosity. Dilute foams of isolated spherical gas cells formed when emulsions were applied to basic surfaces. Gas cells rose to the surface and ruptured, leaving void spaces that penetrated throughout the emulsion. These experiments indicate that emulsions may be a viable means for containing RDD residuals; however, improvements are needed for optimal performance.}, number={10}, journal={Environmental Science and Technology}, author={Fox, G.A. and Medina, V.F.}, year={2005}, pages={3762–3769} }
 @inproceedings{hyporheic and total storage exchange in small sand-bed streams_2005, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-37249074313&partnerID=MN8TOARS}, DOI={10.1061/40792(173)587}, abstractNote={Nutrient processing and carbon storage in stream ecosystems are linked to hydraulic retention. Hydraulic retention refers to the departure of stream flow from ideal “plug flow,” and reflects fluid movement through surface and hyporheic storage zones. Most existing information about hyporheic exchange is based on flume studies or field measurements in relatively steep streams with beds coarser than sand. Stream tracer studies may be used to quantify overall hydraulic retention, but disaggregation of surface and hyporheic retention components remains difficult. A stream tracer approach was used to compute the rates at which stream water is exchanged for water in storage zones (total storage) in short reaches of two small, sand-bed streams. Tracer curves were fit to the one-dimensional transport with inflow storage (OTIS-P) model. Networks of minipiezometers were used to measure hyporheic exchange. The rate of exchange between main channel flow and surface storage zones was assumed equal to the difference between total storage exchange computed by the modeled tracer curves and hyporheic exchange. This technique was used to measure the effects of flow obstructions (large wood) and differences in bed morphology and grain size on surface and hyporheic exchange. Parameters describing total retention were in the upper 50% of data compilations published by others that represent a range of stream sizes and morphologies, but hyporheic exchange was only 0.01% to 0.49% of total exchange. Retention did not correlate to differences in median bed material size, but increased with flow obstruction. Hyporheic storage was an insignificant component of total hydraulic retention in the small sand-bed streams studied.}, booktitle={World Water Congress 2005: Impacts of Global Climate Change - Proceedings of the 2005 World Water and Environmental Resources Congress}, year={2005}, pages={587} }
 @inproceedings{caviness_fox_deliman_2005, title={Modeling the big black river: Evaluation of a simplistic water quality model}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-27844545311&partnerID=MN8TOARS}, booktitle={Proceedings of the 3rd Conference on Watershed Management to Meet Water Quality Standards and Emerging TMDL}, author={Caviness, K.S. and Fox, G.A. and Deliman, P.N.}, year={2005}, pages={467–477} }
 @article{fox_metla_2005, title={Soil property analysis using principal components analysis, soil line, and regression models}, volume={69}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-27644447406&partnerID=MN8TOARS}, DOI={10.2136/sssaj2004.0362}, abstractNote={Past research has attempted to relate surface characteristics of soils to reflectance from remotely sensed images to provide a means for quantifying spatial heterogeneity. Existing procedures have proven valuable, but no research has been performed to compare these techniques. The objective of this research was to compare existing methodologies, that is, principal components analysis (PCA), Chen et al.'s regression model, and the soil line Euclidean distance (SLED) technique, for quantifying spatial heterogeneity in soil surface organic matter (OM) and cation exchange capacity (CEC). The three existing techniques were compared using five bare soil images from three different silt loam to loam fields in the Midwest USA. At the same time as image acquisition, surface (upper 2.54 cm [1 in]) soil properties were measured in situ. Organic matter and CEC were highly correlated (R2 > 0.70) to the first principal component (PC1) for three bare soil images, moderately correlated (R2 > 0.40) for one image, and only slightly correlated (R2 < 0.25) for the final image. The lower correlations were hypothesized to be because of the range in the soil OM and CEC and image exposure. Principal Component 1 accounted for approximately 95% of the total variance in all the fields; therefore, no correlation was observed between the upper 2.54 cm (1‐in) surface soil properties and the second, third, or fourth principal components (PC2, PC3, and PC4, respectively). All three techniques equivalently predicted OM and CEC. However, PCA does not require field‐specific regression or soil lines parameters. It is also suggested that PC1 can replace the soil line in a technique for identifying soil‐sampling locations.}, number={6}, journal={Soil Science Society of America Journal}, author={Fox, G.A. and Metla, R.}, year={2005}, pages={1782–1788} }
 @inproceedings{fox_wilson_periketi_gordji_cullum_2005, place={Oxford, Mississippi, USA}, title={The role of subsurface water in contributing to streambank erosion}, booktitle={Proceedings of the US-China Workshop on Advanced Computational Modeling in Hydroscience and Engineering}, author={Fox, G.A. and Wilson, G.V. and Periketi, R. and Gordji, L. and Cullum, R.F.}, year={2005} }
 @article{fox_sabbagh_searcy_yang_2004, title={An automated soil line identification routine for remotely sensed images}, volume={68}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-3142678094&partnerID=MN8TOARS}, number={4}, journal={Soil Science Society of America Journal}, author={Fox, G.A. and Sabbagh, G.J. and Searcy, S.W. and Yang, C.}, year={2004}, pages={1326–1331} }
 @article{fox_2004, title={Evaluation of a stream aquifer analysis test using analytical solutions and field data}, volume={40}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-4544283745&partnerID=MN8TOARS}, DOI={10.1111/j.1752-1688.2004.tb04457.x}, abstractNote={ABSTRACT:  Considerable advancements have been made in the development of analytical solutions for predicting the effects of pumping wells on adjacent streams and rivers. However, these solutions have not been sufficiently evaluated against field data. The objective of this research is to evaluate the predictive performance of recently proposed analytical solutions for unsteady stream depletion using field data collected during a stream/aquifer analysis test at the Tamarack State Wildlife Area in eastern Colorado. Two primary stream/aquifer interactions exist at the Tamarack site: (1) between the South Platte River and the alluvial aquifer and (2) between a backwater stream and the alluvial aquifer. A pumping test is performed next to the backwater stream channel. Drawdown measured in observation wells is matched to predictions by recently proposed analytical solutions to derive estimates of aquifer and streambed parameters. These estimates are compared to documented aquifer properties and field measured streambed conductivity. The analytical solutions are capable of estimating reasonable values of both aquifer and streambed parameters with one solution capable of simultaneously estimating delayed aquifer yield and stream flow recharge. However, for long term water management, it is reasonable to use simplified analytical solutions not concerned with early‐time delayed yield effects. For this site, changes in the water level in the stream during the test and a varying water level profile at the beginning of the pumping test influence the application of the analytical solutions.}, number={3}, journal={Journal of the American Water Resources Association}, author={Fox, G.A.}, year={2004}, pages={755–763} }
 @article{fox_malone_sabbagh_rojas_2004, title={Interrelationship of macropores and subsurface drainage for conservative tracer and pesticide transport}, volume={33}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-8744229102&partnerID=MN8TOARS}, number={6}, journal={Journal of Environmental Quality}, author={Fox, G.A. and Malone, R. and Sabbagh, G.J. and Rojas, K.}, year={2004}, pages={2281–2289} }
 @inproceedings{stofleth_shields, jr._fox_2004, title={Organic Carbon Concentrations in Hyporheic Zone Sediments: A Tool for Measuring Stream Integrity}, ISBN={9780784407370}, url={http://dx.doi.org/10.1061/40737(2004)416}, DOI={10.1061/40737(2004)416}, abstractNote={Effects of channel incision on sand-bed stream carbon reservoirs were examined. Channel incision may deplete hyporheic zone C stores due to bed erosion, less frequent hydrologic exchanges between stream and floodplain, and paucity of riparian vegetation and large woody debris. Presented are organic C concentrations found in hyporheic sediments before and after an incised stream rehabilitation project and in three adjacent streams in northern Mississippi. The sampled streams comprise a spectrum of physical conditions corresponding to the conceptual channel evolution model (CEM). Carbon concentrations in the upper 10 cm of the bed ranged from 0.24 + 0.36% for a nonincised reference site to only 0.01 + 0.02% for aggradational incised channels. Carbon concentrations generally declined with increase in stage of the CEM, increased with increasing percent canopy over the study reach and were not directly related to large woody debris (LWD) density. These findings suggest factors linking ecological degradation to channel incision and prospective pathways for stream rehabilitation design.}, booktitle={Critical Transitions in Water and Environmental Resources Management}, publisher={American Society of Civil Engineers}, author={Stofleth, John M. and Shields, Jr., F. Douglas and Fox, Garey A.}, year={2004}, month={Jun} }
 @inproceedings{organic carbon concentrations in hyporheic zone sediments: a tool for measuring stream integrity_2004, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-23844474473&partnerID=MN8TOARS}, booktitle={Proceedings of the 2004 World Water and Environmetal Resources Congress: Critical Transitions in Water and Environmetal Resources Management}, year={2004}, pages={4193–4202} }
 @inproceedings{stofleth_shields_fox_2004, place={Salt Lake City, Utah}, title={Organic carbon concentrations in the hyporheic zone: A tool for measuring the effectiveness of stream restoration}, booktitle={Proceedings of the American Society of Civil Engineers (ASCE) Conference of the Water and Environmental Resources Institute}, author={Stofleth, J. and Shields, F.D. and Fox, G.A.}, year={2004} }
 @inproceedings{fox_malone_sabbagh_rojas_2004, place={Fort Collins, Colorado}, title={Simulating the interaction between macropores and subsurface drains with RZWQM}, booktitle={Proceedings of the International Workshop on Applications, Enhancements, and Collaborations of ARS RZWQM and GPFARM Models}, publisher={USDA-ARS Research Great Plains Systems Research Unit}, author={Fox, G.A. and Malone, R. and Sabbagh, G.J. and Rojas, K.}, year={2004}, pages={41–44} }
 @article{hunt_fox_2004, title={“Analytical Model for Aquifer Response Incorporating Distributed Stream Leakage,”by Garey A. Fox, Paul DuChateau, and Deana S. Dumford, July-August 2002 issue, v. 40, no. 4: 378-384.}, volume={42}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0347765873&partnerID=MN8TOARS}, DOI={10.1111/j.1745-6584.2004.tb02463.x}, abstractNote={GroundwaterVolume 42, Issue 1 p. 139-140 “Analytical Model for Aquifer Response Incorporating Distributed Stream Leakage,” by Garey A. Fox, Paul DuChateau, and Deana S. Dumford, July-August 2002 issue, v. 40, no. 4: 378–384. Bruce Hunt, Bruce Hunt Department of Civil Engineering, The University of Canterbury, Christchurch, New Zealand.Search for more papers by this author Bruce Hunt, Bruce Hunt Department of Civil Engineering, The University of Canterbury, Christchurch, New Zealand.Search for more papers by this author First published: 13 December 2005 https://doi.org/10.1111/j.1745-6584.2004.tb02463.xCitations: 5AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume42, Issue1January 2004Pages 139-140 RelatedInformation}, number={1}, journal={Ground Water}, publisher={Wiley}, author={Hunt, B. and Fox, G.A.}, year={2004}, month={Jan}, pages={139–140} }
 @inproceedings{fox_2003, title={Estimating streambed and aquifer parameters from a stream/aquifer analysis test}, booktitle={Proceedings of the 23rd Annual Geophysical Union Hydrology Days}, author={Fox, G.A.}, editor={Ramirez, J.A.Editor}, year={2003}, pages={68–79} }
 @inproceedings{fox_2003, title={Improving MODFLOW’s RIVER package for unsaturated stream/aquifer flow}, booktitle={Proceedings of the 23rd Annual Geophysical Union Hydrology Days}, author={Fox, G.A.}, editor={Ramirez, J.A.Editor}, year={2003}, pages={56–67} }
 @article{fox_sabbagh_searcy_2003, title={Radiometric normalization of multi-temporal images based on image soil lines}, volume={46}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0141790739&partnerID=MN8TOARS}, number={3}, journal={Transactions of the American Society of Agricultural Engineers}, author={Fox, G.A. and Sabbagh, G.J. and Searcy, S.W.}, year={2003}, pages={851–859} }
 @article{fox_durnford_2003, title={Stream Aquifer Analysis Tests: Estimating Aquifer and Streambed Permeability}, volume={20}, number={3}, journal={Colorado Water}, author={Fox, G.A. and Durnford, D.S.}, year={2003}, pages={5–7} }
 @article{fox_durnford_2003, title={Unsaturated hyporheic zone flow in stream/aquifer conjunctive systems}, volume={26}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0042739696&partnerID=MN8TOARS}, DOI={10.1016/S0309-1708(03)00087-3}, abstractNote={Saturated flow is typically assumed for seepage from a stream underlain by an alluvial aquifer. However, if the water table falls a sufficient distance below a semipervious streambed, the head losses in this less conductive layer will cause the region beneath the stream, or hyporheic zone, to become unsaturated. Hyporheic zone flow is defined loosely in this research as the flow that occurs underneath the streambed. Unsaturated flow transforms streams from constant head boundaries to constant flux boundaries, impacting the biogeochemistry in the hyporheic zone. The objective of this paper is to discuss the development and implications of unsaturated flow beneath the streambed. Conditions under which saturated or unsaturated flow occurs and the characteristics of each flow regime are discussed. Next, the effect of unsaturated flow is illustrated for the case of stream leakage induced by a well pumping from an aquifer that is hydraulically interacting with a partially penetrating stream. Prior analytical solutions for alluvial well depletions fail to model unsaturated flow between the streambed and water table. An approximating solution is proposed to estimate aquifer drawdown and stream depletion under saturated/unsaturated hyporheic zone flow conditions.}, number={9}, journal={Advances in Water Resources}, author={Fox, G.A. and Durnford, D.S.}, year={2003}, pages={989–1000} }
 @article{fox_duchateau_dumford_2002, title={Analytical model for aquifer response incorporating distributed stream leakage}, volume={40}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0035987343&partnerID=MN8TOARS}, DOI={10.1111/j.1745-6584.2002.tb02516.x}, abstractNote={Abstract}, number={4}, journal={Ground Water}, author={Fox, G.A. and DuChateau, P. and Dumford, D.S.}, year={2002}, pages={378–384} }
 @inproceedings{fox_dumford_2002, title={Analytical model for saturated/unsaturated hyporheic zone flow due to alluvial well depletions}, booktitle={Proceedings of the American Water Resources Association Specialty Conference on Surface Water/Ground Water Interactions}, author={Fox, G.A. and Dumford, Deanna}, editor={Kenny, J.F.Editor}, year={2002}, pages={479–484} }
 @inproceedings{fox_durnford_2002, title={Effect of aquifer parameter uncertainty on analytical estimates of streambed conductance using STRMAQ}, booktitle={Proceedings of the 22nd Annual Geophysical Union Hydrology Days}, author={Fox, G.A. and Durnford, D.S.}, editor={Ramirez, J.A.Editor}, year={2002}, pages={86–97} }
 @article{fox_sabbagh_2002, title={Estimation of soil organic matter from red and near-infrared remotely sensed data using a soil line Euclidean distance technique}, volume={66}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0036852123&partnerID=MN8TOARS}, number={6}, journal={Soil Science Society of America Journal}, author={Fox, G.A. and Sabbagh, G.J.}, year={2002}, pages={1922–1929} }
 @inproceedings{fox_durnford_2002, place={St. Joseph, Michigan}, title={Unsaturated Hyporheic Zone Flow in Analytical Models for Stream/Aquifer Interaction}, url={http://dx.doi.org/10.13031/2013.9850}, DOI={10.13031/2013.9850}, abstractNote={Pumping from groundwater resources that are hydraulically interactive with adjacent 
streams induces a water flux from the stream to the aquifer. Analytical models of stream/aquifer 
systems assume saturated flow within the region between the streambed and aquifer, or hyporheic 
zone. However, pumping next to a stream may cause the region between the bottom of the 
streambed and the aquifer to become unsaturated. When this perching occurs, the flux from the 
stream to the underlying aquifer approaches a constant limit. Unsaturated, hyporheic zone flow 
transforms streams from constant head boundaries to specific flux boundaries. This research 
presents an analytical solution for drawdown and stream depletion that accounts for unsaturated 
hyporheic zone flow. The saturated and unsaturated hyporheic zone flows are linearly superimposed 
in the analytical model to account for transient stream disconnection along the length of the stream. 
The effect of unsaturated hyporheic zone flow on the total flux from surface water to groundwater will 
be investigated using the proposed analytical solution.}, number={022212022212}, booktitle={2002 Chicago, IL July 28-31, 2002}, publisher={American Society of Agricultural and Biological Engineers}, author={Fox, Garey A. and Durnford, Deanna S.}, year={2002} }
 @inproceedings{fox_durnford_2001, title={Investigation of analytical and numerical models for simulating surface water/groundwater interaction}, booktitle={Proceedings of the 21st Annual Geophysical Union Hydrology Days}, author={Fox, G.A. and Durnford, D.S.}, year={2001}, pages={58–69} }
 @article{sabbagh_fox_1999, title={Statistical method for evaluation of a water table management model}, volume={42}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0033508089&partnerID=MN8TOARS}, number={3}, journal={Transactions of the American Society of Agricultural Engineers}, author={Sabbagh, G.J. and Fox, G.A.}, year={1999}, pages={713–719} }
 @inproceedings{sabbagh_fox_robbins_1998, title={Determination of localized statistical parameters for disaggregation modeling}, number={980027}, booktitle={Papers of the ASAE}, author={Sabbagh, G.J. and Fox, G.A. and Robbins, K.D.}, year={1998} }
 @article{fox_1998, title={Investigation of High Plains management practices with the APEX modeling system}, volume={2}, number={1}, journal={Texas A&M University Undergraduate Journal of Science}, author={Fox, G.A.}, year={1998}, pages={9–16} }
 @article{caviness_fox_deliman, title={MODELING THE BIG BLACK RIVER: EVALUATION OF A SIMPLISTIC WATER QUALITY MODEL}, DOI={10.13031/2013.18108}, abstractNote={The Mississippi Department of Environmental Quality (MDEQ) uses the Steady RiverineEnvironmental Assessment Model (STREAM) to establish permitted effluent limitations forindustrial, commercial, and municipal facilities. While the U.S. Environmental ProtectionAgency (EPA) has approved of its use, questions arise regarding the models simplicity. Thisresearch first evaluated STREAM using a statistical evaluation procedure based on sensitivityanalyses, input probability distribution functions, and Monte Carlo simulation with site-specificdata from a 46-mile reach of the Big Black River in central Mississippi. STREAM reasonablypredicted dissolved oxygen (DO) based on a comparison of output probability distributions withobserved DO. The observed DO was consistently within 80% confidence intervals of modelpredictions. This research also evaluated STREAM by comparing observed DO with predictionsby both STREAM and the Enhanced Stream Water Quality Model (QUAL2E). One version ofthe QUAL2E and STREAM models utilized site-specific input data. A second version of eachmodel involved additional calibration. A third version of STREAM was an uncalibrated modeldeveloped following MDEQ Regulations (1995) for cases where intensive input data areunavailable. All versions of the models were simulated at the 7Q10 flow for the Big BlackRiver, the minimum flow expected for seven consecutive days during a period of ten years.STREAM over predicted while QUAL2E under predicted DO with the site-specific input data.Percent errors ranged between 4.8% and 11.2% for STREAM and 3.3% and 5.1% for QUAL2E.The uncalibrated STREAM model predicted the lowest DO for all scenarios and correspondinglyprovided the most conservative DO predictions.}, journal={Watershed Management to Meet Water Quality Standards and Emerging TMDL, 5-9 March 2005, Atlanta, Georgia}, publisher={American Society of Agricultural and Biological Engineers}, author={Caviness, Kimberly S. and Fox, Garey A. and Deliman, Patrick N.} }