Streambank retreat is a complex cyclical process involving subaerial processes, fluvial erosion, seepage erosion, and geotechnical failures and is driven by several soil properties that themselves are temporally and spatially variable. Therefore, it can be extremely challenging to predict and model the erosion and consequent retreat of streambanks. However, modeling streambank retreat has many important applications, including the design and assessment of mitigation strategies for stream revitalization and stabilization. In order to highlight the current complexities of modeling streambank retreat and to suggest future research areas, this paper reviewed one of the most comprehensive streambank retreat models available, the Bank Stability and Toe Erosion Model (BSTEM), which has recently been integrated with several popular hydrodynamic and sediment transport models including the Hydrologic Engineering Centerˈs River Analysis System (HEC-RAS). The objectives of this paper were to: (i) comprehensively review studies that have utilized BSTEM and report their findings, (ii) address the limitations of the model so that it can be applied appropriately in its current form, and (iii) suggest directions of research that will help make the model a more useful tool in future applications. The paper includes an extensive overview of peer reviewed studies to guide future users of BSTEM. The review demonstrated that the model needs further testing and evaluation outside of the central United States. Also, further development is needed in terms of accounting for spatial and temporal variability in geotechnical and fluvial erodibility parameters, incorporating subaerial processes, and accounting for the influence of riparian vegetation on streambank pore-water pressure dynamics, applied shear stress, and erodibility parameters.

Abstract. The future reliance on water supply and flood control reservoirs across the globe will continue to expand, especially under a variable climate. 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 sediment transport rates and loading due to streambank and gully erosion within a watershed. For example, additional in-stream 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 in-stream 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 a better understanding of 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.

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Ecohydrology combines empiricism, data analytics, and the integration of models to characterize linkages between ecological and hydrological processes. A challenge for practitioners is determining which models best generalizes heterogeneity in hydrological behaviour, including water fluxes across spatial and temporal scales, integrating environmental and socio‐economic activities to determine best watershed management practices and data requirements. We conducted a literature review and synthesis of hydrologic, hydraulic, water quality, and ecological models designed for solving interdisciplinary questions. We reviewed 1,275 papers and identified 178 models that have the capacity to answer an array of research questions about ecohydrology or ecohydraulics. Of these models, 43 were commonly applied due to their versatility, accessibility, user‐friendliness, and excellent user‐support. Forty‐one of 43 reviewed models were linked to at least 1 other model especially: Water Quality Analysis Simulation Program (linked to 21 other models), Soil and Water Assessment Tool (19), and Hydrologic Engineering Center's River Analysis System (15). However, model integration was still relatively infrequent. There was substantial variation in model applications, possibly an artefact of the regional focus of research questions, simplicity of use, quality of user‐support efforts, or a limited understanding of model applicability. Simply increasing the interoperability of model platforms, transformation of models to user‐friendly forms, increasing user‐support, defining the reliability and risk associated with model results, and increasing awareness of model applicability may promote increased use of models across subdisciplines. Nonetheless, the current availability of models allows an array of interdisciplinary questions to be addressed, and model choice relates to several factors including research objective, model complexity, ability to link to other models, and interface choice.

Abstract. An analysis of the long term morphological evolution of the Génissiat reservoir (France) is provided. First, a methodology for bathymetric data processing and reservoir sediment volume budget calculation is described. An estimation of global uncertainties in volume calculation is proposed. The reservoir bathymetric budget for several dam flushing events and interflush periods is presented, showing the global decrease of deposited sediment volume with time. The spatial dynamics of the reservoir subreaches is highlighted and typical patterns in flush and interflush periods are identified.

Preferential flow in soils contributes to water and contaminant leaching to groundwater and subsurface drains. At practical scales, preferential flow is often neglected due to the lack of consensus or guidance on how to simulate this process. Dual-permeability (DP) approaches are a standard, but their applicability in practice is limited by the large number of parameters involved. The sourceresponsive (SR) model simulates preferential flow as flow films along the walls of macropores that interact with the soil matrix. The objective of this study was to evaluate the ability of the SR model and a DP model with calibration limited to macropore parameters to simulate hydrologic variables of interest for practical applications. Infiltration experiments were conducted in a 150-cm-long by 50-cm-wide by 40-cm-deep soil column with vertical artificial macropores, with preferential flow being the most prevalent flow process. Two macropore configurations and various rainfall rates were tested. The DP model provided relatively accurate predictions of the bottom drainage rates, but inaccurate soil parameter estimates resulted in poor predictions of matrix flow. Critical limitations in the SR model formulation were highlighted, and the model was revised. The refined SR model provided accurate predictions of bottom drainage rates and water contents under steady-state rainfall. The DP model with a reduced calibration appeared valid to estimate subsurface fluxes with negligible matrix flow. The SR model applicability is limited to steady-state scenarios with negligible matrix flow. Critical developments are needed for the SR model to be applicable in practice. 1 INTRODUCTION Preferential flow through soil macropores promotes the fast downward movement of water, solutes, and small par-Abbreviations: DP, dual-permeability; REV, representative element volume; SR, source-responsive This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Abstract: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 (τ c ) and the erodibility coefficient (k d ) for the excess shear stress model and b 0 and b 1 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.