@article{shahriar_gabr_montoya_ortiz_2023, title={Estimating live-bed local scour around bridge piers in cohesionless sediments: applicability and bias of selected models}, volume={60}, ISSN={["1208-6010"]}, url={http://dx.doi.org/10.1139/cgj-2022-0122}, DOI={10.1139/cgj-2022-0122}, abstractNote={ To design the foundation system of waterway bridges, Load and Resistance Factor Design guidelines suggest use of deterministic scour depth prediction models. Understanding the inherent bias of deterministic scour depth prediction models will advance the development of reliability index-based foundation design regime. Four bridge scour depth prediction models were assessed in terms of two statistical parameters, termed herein mean absolute percentage error (MAPE), and conservatism, percentage of cases the predicted scour depth exceeded the measured scour depth. Live-bed laboratory and field scour depth databases were used in analyses to quantify model scatter by comparatively assessing the computed scour depth versus measured data. For live-bed laboratory data, values of MAPE ranged from 23.5% to 59.8%, whereas conservatism ranged from 28.4% to 97.8%. For live-bed field data, conservatism varied from 93.3% to 95.1%, while MAPE ranged from 205.6% to 319%. Statistical models were applied to ascertain the biasness of the four deterministic models. Accuracy and conservatism of a given model were consequently adjusted through proposed modification factors. The proposed approach allows for the selection of a suitable modification factor to satisfy a target probability of deceedance or a target conservatism. }, number={4}, journal={CANADIAN GEOTECHNICAL JOURNAL}, publisher={Canadian Science Publishing}, author={Shahriar, Azmayeen R. and Gabr, Mohammed A. and Montoya, Brina M. and Ortiz, Alejandra C.}, year={2023}, month={Apr}, pages={471–487} }
 @article{johnson_ortiz_2023, title={Finding patterns of atoll morphometrics at a range of spatial scales}, volume={11}, ISSN={["2296-6463"]}, DOI={10.3389/feart.2023.1123339}, abstractNote={Small Island Nations, often comprised of Atolls, are at considerable risk of climate change impacts from sea-level rise to coral acidification to increasing cyclone intensity; understanding how they will change in the coming century is vital for climate mitigation and resiliency. However, the morphology of atolls are not well quantified or summarized. In this work, we calculate modern atoll morphometrics on a global scale including 3,786 motu and 593 reef flats on 154 atolls. Temporal composites of Landsat imagery are created for 4 years (2015–2018), and are classified into motu, reef flat, open water/lagoon via unsupervised classification. Morphometrics, including widths, lengths, and area, are computed for each motu and reef flat of the atoll in Python, creating a database of atolls and their associated morphometrics. Consistency in automated processing of atoll morphometrics removes spatial and user bias, enabling a better understanding of geographic patterns of atoll area and other morphometrics. Distinct differences in the distribution of motu are seen on a regional scale in French Polynesia, while globally, wider reef flats and larger motu are found closest to the equator. Globally, there is a consistent reef flat width in front of large motu (>1 km length) of 184 ± 93 m (n = 724). Our atoll morphometric database creates a baseline of current atoll characteristics that can be expanded upon in the future and used for evaluating temporal changes to atoll islands.}, journal={FRONTIERS IN EARTH SCIENCE}, author={Johnson, Faith M. and Ortiz, Alejandra C.}, year={2023}, month={Mar} }
 @article{shahriar_gabr_montoya_ortiz_2023, title={Framework for a reliability-based analysis of local scour and its effect on pile response in clay}, volume={153}, ISSN={0266-352X}, url={http://dx.doi.org/10.1016/j.compgeo.2022.105093}, DOI={10.1016/j.compgeo.2022.105093}, abstractNote={The analyses of axial and lateral capacity of a pile are significantly dependent on the appropriate estimation of scour depth, while the scour depth estimation procedure is uncertain due to the hydraulic, hydrologic, and geotechnical parameters uncertainty. Work herein is focused on developing a framework for reliability-based pier scour assessment methodology and demonstrate its integration with the concept of Load and Resistance Factor Design (LRFD) approach. Scour factors are proposed based on reliability level ( β ) and the associated probability of deceedance (POD). Three example applications of axially and laterally loaded pile design approach while including scour factor in the LRFD framework are demonstrated. Based on axial pile capacity analysis, the increase of pile length when the β -based scour assessment is used with the soil resistance factors, was estimated to be 26.5–29.6 % higher compared to using the deterministic scour with soil resistance factor. In the case of lateral pile response analysis, as β is increased from 2.0 to 3.0, the lateral pile head deflection increased by 46–132 % compared to the deterministically-estimated scour depth case. To obtain β = 3.0 for the considered example while maintaining the pile length unchanged, the pile diameter needed to be increased by 35.7 % compared to the base case pile’s diameter.}, journal={Computers and Geotechnics}, publisher={Elsevier BV}, author={Shahriar, Azmayeen R. and Gabr, Mohammed A. and Montoya, Brina M. and Ortiz, Alejandra C.}, year={2023}, month={Jan}, pages={105093} }
 @article{shahriar_gabr_montoya_ortiz_2023, title={Local scour around bridge abutments: Assessment of accuracy and conservatism}, volume={619}, ISSN={["1879-2707"]}, url={https://doi.org/10.1016/j.jhydrol.2023.129280}, DOI={10.1016/j.jhydrol.2023.129280}, abstractNote={More than 80 percent of the bridges in the United States are built over waterways. The support systems of the structures crossing waterways are subjected to scour during their service life owing to the flowing water-induced bed shear stresses, resulting in scour. Work herein is focused on characterizing the error associated with three abutment scour prediction models included in the Hydraulic Engineering Circular No. 18. An abutment scour database is utilized to quantify the predicted versus the measured scour depth relationship. Abutment scour prediction models are assessed in terms of two statistical parameters, termed herein Mean Absolute Percentage Error (MAPE, as a measure of accuracy of the prediction), and Level of conservatism, (defined as percentage of cases for which the predicted scour exceeded the measured scour.) For scour associated with vertical wall and spill through abutments, responses to long abutment, and intermediate abutment are examined separately. For vertical wall abutments, conservatism ranged from 4.76% to 100%, and MAPE ranged from 44% to 201%. For spill through abutments, conservatism ranged from 0% to 100%, and MAPE ranged from 10.3% to 347%. Comprehension of the accuracy and conservatism of the deterministic models considered herein contributes to understanding the limitation of the scour depth prediction models.}, journal={JOURNAL OF HYDROLOGY}, author={Shahriar, Azmayeen R. and Gabr, Mohammed A. and Montoya, Brina M. and Ortiz, Alejandra C.}, year={2023}, month={Apr} }
 @article{shahriar_ortiz_montoya_gabr_2021, title={Bridge Pier Scour: An overview of factors affecting the phenomenon and comparative evaluation of selected models}, volume={28}, ISSN={2214-3912}, url={http://dx.doi.org/10.1016/j.trgeo.2021.100549}, DOI={10.1016/j.trgeo.2021.100549}, abstractNote={Scour, defined by the loss of geomaterials surrounding a foundation support system, is a primary cause of bridge failure in the United States and worldwide. Work herein presents a comprehensive review of the current state of knowledge on geotechnical aspects of erodibility, factors influencing pier scour, factors complicating pier scour assessment, and databases available on erodibility and pier scour. A summary of deterministic pier scour models, developed since 1990, is presented in view of the factors affecting scour rate and equilibrium magnitude. The study discusses challenges in the predictive approaches reviewed in the paper. In addition, advancements in probabilistic pier scour models, and observation-based models are summarized. Four pier scour models, namely Wilson (1995) model, Melville (1997) model, Hydraulic Engineering Circular No. 18 (2012) model, and Briaud (2014) model are comparatively applied to data from laboratory pier scour database. Error statistics and accuracy, precision, and probabilistic distribution of predictions from these models are presented and discussed.}, journal={Transportation Geotechnics}, publisher={Elsevier BV}, author={Shahriar, Azmayeen R. and Ortiz, Alejandra C. and Montoya, Brina M. and Gabr, Mohammed A.}, year={2021}, month={May}, pages={100549} }
 @article{shahriar_montoya_ortiz_gabr_2021, title={Quantifying probability of deceedance estimates of clear water local scour around bridge piers}, volume={597}, ISSN={0022-1694}, url={http://dx.doi.org/10.1016/j.jhydrol.2021.126177}, DOI={10.1016/j.jhydrol.2021.126177}, abstractNote={Local bridge scour, which is defined as the loss of soil particles/mass surrounding a pier foundation due to the flowing water-induced shear stresses, is a primary cause of bridge failure in the United States and worldwide. Current practice of bridge scour prediction is mostly based on the use of deterministic models. Work herein presents statistical models that extend five deterministic approaches reported in literature to predict the expected scour depth while quantifying inherent model bias and uncertainty in view of data scatter. Clear water scour database is used herein and the analyses quantify model scatter by comparatively assessing the computed scour depth versus measured data reported in the database. A relationship between probability of deceedance associated with the predicted scour depth and a modification factor (that is applied into the deterministic prediction) is devised. The modification factor allows for the use of the scour magnitude computed from the deterministic models while quantifying the probability of a computed scour depth being less than or more than a most likely value (per measurements reported in the database). The application of the proposed model is demonstrated with an example and the results are discussed.}, journal={Journal of Hydrology}, publisher={Elsevier BV}, author={Shahriar, Azmayeen R. and Montoya, Brina M. and Ortiz, Alejandra C. and Gabr, Mohammed A.}, year={2021}, month={Jun}, pages={126177} }
 @article{ortiz_roy_edmonds_2017, title={Land loss by pond expansion on the Mississippi River Delta Plain}, volume={44}, ISSN={["1944-8007"]}, DOI={10.1002/2017gl073079}, abstractNote={Abstract}, number={8}, journal={GEOPHYSICAL RESEARCH LETTERS}, author={Ortiz, Alejandra C. and Roy, Samapriya and Edmonds, Douglas A.}, year={2017}, month={Apr}, pages={3635–3642} }
 @article{ortiz_ashton_2016, title={Exploring shoreface dynamics and a mechanistic explanation for a morphodynamic depth of closure}, volume={121}, ISSN={2169-9003}, url={http://dx.doi.org/10.1002/2015JF003699}, DOI={10.1002/2015JF003699}, abstractNote={Abstract}, number={2}, journal={Journal of Geophysical Research: Earth Surface}, publisher={American Geophysical Union (AGU)}, author={Ortiz, Alejandra C. and Ashton, Andrew D.}, year={2016}, month={Feb}, pages={442–464} }
 @article{ortiz_ashton_nepf_2013, title={Mean and turbulent velocity fields near rigid and flexible plants and the implications for deposition}, volume={118}, ISSN={2169-9003}, url={http://dx.doi.org/10.1002/2013JF002858}, DOI={10.1002/2013JF002858}, abstractNote={The transport of fine sediment and organic matter plays an important role in the nutrient dynamics of shallow aquatic systems, and the fate of these particles is closely linked to vegetation. We describe the mean and turbulent flow near circular patches of synthetic vegetation and examine how the spatial distribution of flow is connected to the spatial distribution of suspended sediment deposition. Patches of rigid, emergent, and flexible, submerged vegetation were considered, with two different stem densities. For the rigid emergent vegetation, flow adjustment was primarily two‐dimensional, with flow deflected in the horizontal plane. Horizontal shear layers produced a von Kármán vortex street. Flow through the patch shifted the vortex street downstream, resulting in a region directly downstream of the patch in which both the mean and turbulent velocities were diminished. Net deposition was enhanced within this region. In contrast, for the flexible, submerged vegetation, flow adjustment was three‐dimensional, with shear layers formed in the vertical and horizontal planes. Because of strong vertical circulation, turbulent kinetic energy was elevated directly downstream of the patch. Consistent with this, deposition was not enhanced at any point in the wake. This comparison suggests that morphological feedbacks differ between submerged and emergent vegetation. Further, enhanced deposition occurred only in regions where both turbulent and mean velocities were reduced, relative to the open channel. Reduced deposition (indicating enhanced resuspension) occurred in regions of high turbulence kinetic energy, regardless of local mean velocity. These observations highlight the importance of turbulence in controlling deposition.}, number={4}, journal={Journal of Geophysical Research: Earth Surface}, publisher={American Geophysical Union (AGU)}, author={Ortiz, Alejandra C. and Ashton, Andrew and Nepf, Heidi}, year={2013}, month={Dec}, pages={2585–2599} }
 @article{chen_ortiz_zong_nepf_2012, title={The wake structure behind a porous obstruction and its implications for deposition near a finite patch of emergent vegetation}, volume={48}, ISSN={0043-1397}, url={http://dx.doi.org/10.1029/2012WR012224}, DOI={10.1029/2012WR012224}, abstractNote={This experimental study describes the mean and turbulent flow structure in the wake of a circular array of cylinders, which is a model for a patch of emergent vegetation. The patch diameter, D, and patch density, a (frontal area per volume), are varied. The flow structure is linked to a nondimensional flow blockage parameter, CDaD, which is the ratio of the patch diameter and a drag length scale (CDa)−1. CD is the cylinder drag coefficient. The velocity exiting the patch, Ue, is reduced relative to the upstream velocity, U∞, and Ue/U∞ decreases as flow blockage (CDaD) increases. A predictive model is developed for Ue/U∞. The wake behind the patch contains two peaks in turbulence intensity. The first peak occurs directly behind the patch and is related to turbulence production within the patch at the scale of individual cylinders. The second peak in turbulence intensity occurs at distance Lwdownstream from the patch and is related to the wake‐scale vortices of the von Karman vortex street. The presence of the flowUe in the wake delays the formation of the von Karman vortex street until distance L1 (<Lw) behind the patch. Both L1 and Lw increase as Ue increases and thus as the flow blockage (CDaD) decreases. L1sets the distance behind the patch within which fine‐particle deposition can occur. BeyondLw, turbulence associated with the wake‐scale vortices inhibits deposition.}, number={9}, journal={Water Resources Research}, publisher={American Geophysical Union (AGU)}, author={Chen, Zhengbing and Ortiz, Alejandra and Zong, Lijun and Nepf, Heidi}, year={2012}, month={Sep} }