Submitted to: Mississippi Water Resources Research Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/15/2009
Publication Date: 2/1/2010
Citation: Ramirez-Avila, J.J., Langendoen, E.J., Mcanally, W.H., Martin, J.L., Ortega-Achury, S.L., Diaz-Ramirez, J.N. 2010. Identification of streambank erosion processes and channel changes in northeastern Mississippi. Mississippi Water Resources Research Conference Proceedings. 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 streambanks. In order to develop practices to reduce the detrimental impact of the increased stream bank loadings on downstream habitat and infrastructure, it is necessary to understand the processes that control stream bank erosion and the resulting types of stream bank erosion. 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 are collecting a comprehensive data set of bank material properties and erosion rates along selected reaches of Town Creek. Preliminary analysis shows that streambank erosion in the northern headwaters is dominated by bank collapse processes and subsequent removal of failed materials during storm flow events. The downstream reaches are more stable with bank erosion primarily due to scouring by flowing water with limited contributions from mass failures. The improved understanding of how bank erosion differs along Town Creek can be used by federal, state, and local action agencies to develop more effective, targeted practices to reduce stream bank erosion.
Technical Abstract: Identification of streambank erosion processes is important for determining suitable measurement techniques and for choosing appropriate stream remedial measures. Sediment loads from watersheds located in Northeastern Mississippi can have contributions from stream channel degradation as large as 90%. Town Creek watershed is an experimental watershed in the Southeastern Plain Ecoregion of Mississippi (Ecoregion 65). Northern headwaters in Town Creek located within the Black Prairie Subecoregion present incised streams with unstable active bank profiles. The most common gravitational failure mechanisms are slab failure, soil fall, and cantilever failure, accompanied by a basal clean out process when stormflow events occur. An active agricultural land use near streambanks with limited or reduced presence of riparian zones increases the streambank instability and favors gully erosion activity. This condition is predominant along the different headwater reaches. The middle 20 km of the principal channel system is located within the transitional zone between the Tombigbee Hills and the Black Prairie subecoregions. Wide stable channels showing evidence of streambank erosion induced by fluvial erosion, shallow slides, and rotational failures are mixed with natural, vegetated zones and regions with sediment deposition on bed and streambanks. Especially along this section of the principal channel, sediment bed deposition and erosion are significantly modified seasonally by flow conditions. Low flow velocities and sediment deposition occur on the inside of incipient meander bends in the sinuous reach, along the downstream most 10 km before the outlet at the Tombigbee River.