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Quantifying and Modeling Sediment Loads from Streambank Erosion along the Headwaters of Town Creek in Mississippi

Ramirez-Avila, J. J., Langendoen, E. J., McAnally, W. H., Martin, James L., & Ortega-Achury, S. L. (2015). Quantifying and Modeling Sediment Loads from Streambank Erosion along the Headwaters of Town Creek in Mississippi. Federal Interagency Sedimentation Conferences (FISC). Reno, NV.

Abstract

The prediction of erosion is an important component in the development of land management strategies, particularly where sediment is identified as the cause of water quality impairment. Computational models that predict streambank erosion allow the user not only to quantify the streambank erosion rates and processes along a stream, but also to take subsequent decisions regarding sediment loads reduction, especially when those decisions need to pay special attention to stream channel processes and stabilization of eroding reaches. Streambank erosion processes were hypothesized to be an important mechanism driving sediment supply from the Town Creek Watershed in Mississippi. Field monitoring observations along the main channel of the Town Creek and several of its tributaries have indicated that the incised headwaters can contribute up to 70% of the suspended sediment loads exported by the watershed. Observations also evidenced that annual streambank retreat rates and loads in the Town Creek headwaters could be as high as 2.67 m and 28.5 Mg per meter of stream length, respectively. Thus, streambanks were a significant source of sediments loads to the Tombigbee River and the Aberdeen Pool on the Tennessee-Tombigbee Waterway. The ability of the Conservational Channel Evolution and Pollutant Transport System (CONCEPTS) computer model to predict streambank erosion along the Town Creek Watershed in MS was tested through its application to a 270-m long headwater incised reach. Model predictions over a 13 month period were compared with cross section surveys at 8 transects along the modeling reach. Results showed that CONCEPTS accurately predicted top width retreat and streambank failures in time and magnitude. Results from field monitoring and computational modeling offer important insights into the relative effects of land and streambank erosion on the stream water quality and sediment budget for Town Creek Watershed. Reduction of suspended sediment loads should focus on the attenuation of geomorphic processes and stabilization of reaches and agricultural lands near streambanks at the headwaters within the watershed.


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