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Title: Quantifying and modeling sediment loads from streambank erosion along the headwaters of Town Creek in Mississippi

Author
item RAMIREZ-AVILA, JOHN - Mississippi State University
item Langendoen, Eddy
item MCANALLY, WILLIAM - Mississippi State University
item MARTIN, JAMES - Mississippi State University
item ORTEGA-ACHURY, SANDRA - Mississippi State University
item Bingner, Ronald - Ron

Submitted to: Federal Interagency Sedimentation Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/26/2015
Publication Date: 4/19/2015
Citation: Ramirez-Avila, J.J., Langendoen, E.J., Mcanally, W., Martin, J.L., Ortega-Achury, S.L., Bingner, R.L. 2015. Quantifying and modeling sediment loads from streambank erosion along the headwaters of Town Creek in Mississippi. 3rd Joint Federal Interagency Sedimentation Conference Proceedings. April 19-23, 2015, Reno, NV, pp.1907-1918.

Interpretive Summary: Stream channels in the Town Creek watershed in northeastern Mississippi were channelized in the early 20th century to improve drainage of the adjacent floodplain for cultivation and increase transport of sediments eroded from the adjacent hill slopes. The consequent unnatural channel form has caused an acceleration of erosional processes, especially eroding fine-grained sediments from stream banks causing navigation problems downstream on the Tennessee-Tombigbee Waterway. Because the prediction of erosion is an important component in the development of land management strategies, researchers at the U.S. Department of Agriculture-Agricultural Research Service-National Sedimentation Laboratory and the Department of Civil and Environmental Engineering of Mississippi State University have evaluated the ability of the USDA Conservational Channel Evolution and Pollutant Transport System (CONCEPTS) computer model to predict stream bank erosion along the Town Creek Watershed. Model predictions over a 13 month period were compared with cross section surveys at 8 transects along an incised reach. Results showed that CONCEPTS accurately predicted top bank retreat and timings and magnitudes of stream bank failures. Results from field monitoring and computational modeling offered important insights into the relative effects of land and stream bank erosion on the stream water quality and sediment budget for Town Creek Watershed. Further, reduction of suspended sediment loads should focus on the stabilization of reaches and agricultural lands near stream banks along the headwaters of the watershed.

Technical 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.