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Title: Bank stability analysis for fluvial erosion and mass failure

Author
item PAPANICOLAOU, ATHANASIOS - University Of Tennessee
item SUTARTO, TOMMY - Samarinda Polytechnic State University
item WILSON, CHRISTOPHER - University Of Tennessee
item Langendoen, Eddy

Submitted to: Proceedings of the World Environmental and Water Resources Congress Conference
Publication Type: Proceedings
Publication Acceptance Date: 4/15/2014
Publication Date: 5/16/2014
Citation: Papanicolaou, A.N., Sutarto, T.E., Wilson, C.G., Langendoen, E.J. 2014. Bank stability analysis for fluvial erosion and mass failure. In: Proceedings of the World Environmental and Water Resources Congress Conference. 1497-1508. doi:10.1061/9780784413548.150.

Interpretive Summary: Streambanks retreat through combined fluvial erosion by the flowing water and mass failure by gravitational forces. The magnitude of the erosion resistance of the bank soils for each retreat mode can be quite different. The designing of effective bank protection measures needs to account for these differences in soil erosion resistance. Scientists at the USDA, ARS, National Sedimentation Laboratory in collaboration with researchers at the University of Iowa analyzed a total of 24 streambank samples from a representative stream in the U.S. Midwest (i.e., Clear Creek, IA) with semi-cohesive soils in terms of both mechanical and fluvial erosional strength. Mechanical strength was measured using a direct shear device and ranged from 400 to 6,600 Pa. Fluvial erosional strength was measured using a conduit flume, which applied a shearing force to the sample and had values between 1.28 and 2.37 Pa. Thus, mechanical strength was two to three orders of magnitude larger than fluvial erosional strength, which suggests that identifying the different modes of streambank erosion (e.g., mechanical or fluvial) during a hydrograph is needed to provide better design specifications for bank stabilization practices.. This information is useful for stream-restoration practitioners active in the design of stable stream banks for developing appropriate bank-soil property data collection strategies and for improving the accuracy of streambank stability analyses.

Technical Abstract: The central objective of this study was to highlight the differences in magnitude between mechanical and fluvial streambank erosional strength with the purpose of developing a more comprehensive bank stability analysis. Mechanical erosion and ultimately failure signifies the general movement or collapse of large soil blocks due to geotechnical instability and is the upper limit of streambank erosion. Conversely, fluvial erosion is the detachment of individual particles or aggregates due to the shearing action of flow and is the lower limit of streambank erosion. A total of 24 streambank samples from a representative stream in the U.S. Midwest (i.e., Clear Creek, IA) with semi-cohesive soils were analyzed in terms of both mechanical and fluvial erosional strength. Mechanical strength was measured using a direct shear device and ranged from 400 to 6,600 Pa. Fluvial erosional strength was measured using a conduit flume, which applied a shearing force to the sample and had values between 1.28 and 2.37 Pa. Thus, mechanical strength was two to three orders of magnitude larger than fluvial erosional strength, which suggests that identifying the different modes of streambank erosion (e.g., mechanical or fluvial) during a hydrograph is needed to provide better design specifications for bank stabilization practices.