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Title: Modeling sediment mobilization using a distributed hydrological model coupled with a bank stability model: MODELING SEDIMENT MOBILI
Author(s) / Creator(s):
 ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Water Resources Research
Page Range / eLocation ID:
2051 to 2073
Medium: X
Sponsoring Org:
National Science Foundation
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  1. Abstract Purpose The equilibrium sediment exchange process is defined as instantaneous deposition of suspended sediment to the streambed countered by equal erosion of sediment from the streambed. Equilibrium exchange has rarely been included in sediment transport studies but is needed when the sediment continuum is used to investigate the earth’s critical zone. Materials and methods Numericalmodeling in the watershed uplands and streamcorridor simulates sediment yield and sediment source partitioning for the Upper South Elkhorn watershed in Kentucky, USA.We simulate equilibrium exchange when uplandderived sediment simultaneously deposits to the streambed while streambed sediments erode. Sediment fingerprinting with stable carbon isotopes allowed constraint of the process in a gently rolling watershed. Results and discussion Carbon isotopes work well to partition upland sediment versus streambed sediment because sediment deposited in the streambed accrues a unique autotrophic, i.e., algal, fingerprint. Stable nitrogen isotopes do not work well to partition the sources in this study because the nitrogen isotope fingerprint of algae falls in the middle of the nitrogen isotope fingerprint of upland sediment. The source of sediment depends on flow intensity for the gently rolling watershed. Streambed sediments dominate the fluvial load for low and moderate events, while upland sediments become increasingly important during high flows and extreme events.We used sediment fingerprinting results to calibrate the equilibrium sediment exchange rate in the watershed sediment transport model. Conclusions Our sediment fingerprinting and modeling evidence suggest equilibrium sediment exchange is a substantial process occurring in the system studied. The process does not change the sediment load or streambed sediment storage but does impact the quality of sediment residing in the streambed. Therefore, we suggest equilibrium sediment exchange should be considered when the sediment continuumis used to investigate the critical zone.We conclude the paper by outlining future research priorities for coupling sediment fingerprinting with watershed modeling. 
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  2. Abstract

    Sediment regimes, i.e., the processes that recruit, transport, and store sediment, create the physical habitats that underpin river‐floodplain ecosystems. Natural and human‐induced disturbances that alter sediment regimes can have cascading effects on river and floodplain morphology, ecosystems, and a river's ability to provide ecosystem services, yet prediction of the response of sediment dynamics to disturbance is challenging. We developed the Sediment Routing and Floodplain Exchange (SeRFE) model, which is a network‐based, spatially explicit framework for modeling sediment recruitment to and subsequent transport through drainage networks. SeRFE additionally tracks the spatially and temporally variable balance between sediment supply and transport capacity. Simulations using SeRFE can account for various types of watershed disturbance and for channel‐floodplain sediment exchange. SeRFE is simple, adaptable, and can be run with widely available geospatial data and limited field data. The model is driven by real or user‐generated hydrographs, allowing the user to assess the combined effects of disturbance, channel‐floodplain interactions and particular flow scenarios on the propagation of disturbances throughout a drainage network, and the resulting impacts to reaches of interest. We tested the model in the Santa Clara River basin, Southern California, in subbasins affected by large dams and wildfire. Model results highlight the importance of hydrologic conditions on postwildfire sediment yield and illustrate the spatial extent of dam‐induced sediment deficit during a flood. SeRFE can provide contextual information on reach‐scale sediment balance conditions, sensitivity to altered sediment regimes, and potential for morphologic change for managers and practitioners working in disturbed watersheds.

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