Submitted to: International Conference on Water Resources Engineering Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/1/1999
Publication Date: N/A
Interpretive Summary: Degrading stream systems have a major impact on riparian ecology and the amount of sediment eroded from the channel boundaries due to failure of the streambanks. The ability to understand the mechanics of bank erosion processes is an important step in mitigating such impacts. An improved and comprehensive computer simulation model has been developed to predict the moment a streambank becomes unstable and the dimensions of the block of soil falling from the streambank. Among others, the model takes into account forces exerted by the water in the channel and in the streambank itself. The model has been validated using data collected at a monitoring site on the Goodwin Creek, northern Mississippi. The model accurately predicted several bank failures at the monitoring site between March 1996 and March 1997. This model can be used by agencies such as USDA-NRCS and US Army Corps of Engineers to design and evaluate stream stabilization measures.
Technical Abstract: Streambank erosion is a major contributor to total erosion in disturbed landscapes. Identification of the dominant streambank erosion processes and their conceptualization in mathematical width adjustment models remain very difficult tasks. The U.S. Department of Agriculture, Agricultural Research Service, National Sedimentation Laboratory (NSL) conducts field studies to characterize the impact of pore-water pressures on failure dimensions and shearing resistance, and the role of riparian vegetation on matric suction, streambank permeability, and shearing resistance. Results from these studies are used to enhance the NSL's long-term channel evolution model CONCEPTS. This paper discusses the implementation of the above physical processes for bank failures along planar slip surfaces, and demonstrates the ability of CONCEPTS to simulate streambank failure processes. The proposed streambank-stability scheme accurately predicts timing and dimensions of bank failures along a bendway in the Goodwin Creek, Mississippi between March 1, 1996 and March 31, 1997. Differences between predicted and observed top-bank retreat (up to 40%) are caused by the observed cantilever failure of the streambank, yielding a large failure plane angle.