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Title: Assessment and estimation of streambank erosion rates in the Southeastern Plains ecoregion of 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

Submitted to: Federal Interagency Sedimentation Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/1/2010
Publication Date: 6/27/2010
Citation: Ramirez-Avila, J.J., Langendoen, E.J., Mcanally, W.H., Martin, J.L., Ortega-Achury, S.L. 2010. Assessment and estimation of streambank erosion rates in the Southeastern Plains ecoregion of Mississippi. Federal Interagency Sedimentation Conference Proceedings.

Interpretive Summary: Many streams 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 affect of bank soil physical properties on erosion rates. 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 collected a comprehensive data set of bank material properties and erosion rates along selected reaches of Town Creek located in northeastern Mississippi. This data set is used to develop relationships between bank material properties and bank erosion rates for streams in the Southeastern Plain Ecoregion. Preliminary analysis showed stream bank materials to be highly erodible and to vary significantly along the stream. Erosion rates greatly depended on the presence of riparian vegetation, channel runoff and channel form. The improved understanding of how bank erosion relates to soil properties, runoff, location within the watershed, and management of the riparian zone can be used by federal, state, and local action agencies to develop more effective practices to reduce stream bank erosion.

Technical Abstract: Sediment loads from watersheds located in the Southeastern Plain Ecoregion can have contributions from stream channel degradation as large as 90%. Monitoring and modeling techniques to assess the contribution of channel sediment to overall sediment load are needed to determine the reductions necessary to meet water quality standards. A study is performed with the main objective to evaluate streambank erosion rates and generate empirical correlations for estimating streambank surface erosion involving physical and geomorphic variables influencing this process for streams in the Southeastern Plains Ecoregion in Mississippi. Focusing on the Town Creek watershed in this ecoregion the study used a combination of methods including field reconnaissance and detailed data collection, surveying, and channel modeling. Watershed characterization and preliminary reports showed increased rates of sediments emanating from the northern headwaters of the watershed. Incised streams with unstable active streambank profiles near agricultural lands and limited or no riparian vegetation are common in the northern headwaters. Streambank failure events tend to be periodic and mainly occur during runoff season. Channel morphology changes from incised V-shaped channels to wide U-shaped channels with an accompanying increase in riparian vegetation density along the middle 20-km of the principal channel. Streambank erosion pin data along the middle 20-km of the principal channel showed negative average erosion depths (i.e., deposition) at most of the erosion pin plots. Although, jet tests showed streambank soils to be highly erodible. Preliminary results of watershed characterization and field observation show that streambank erosion and deposition rates are largely seasonal and depend on channel morphology.