Semester

Summer

Date of Graduation

2011

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Wildlife and Fisheries Resources

Committee Chair

Nicolas Zegre.

Abstract

Factors and processes influencing streambank erosion are not fully understood and combining factors and processes into a model that predicts streambank erosion is difficult. The mechanistic Bank Stability and Toe Erosion Model (BSTEM) and the empirical Bank Assessment of Nonpoint Source Consequences of Sediment (BANCS) model were evaluated to determine their effectiveness at predicting or explaining streambank erosion along Horseshoe Run. BSTEM underpredicted erosion by between 60 and 75%, but the model was able to provide relative estimates of eroded material and was also able to predict the type of erosion present at most bank sites. Model validation revealed critical shear stress of the bed material to be locally specific and non transferable to neighboring sites on the same stream. The input parameters for the BANCS model may be used to explain the susceptibility of a streambank to erosion. However, careful consideration needs to be given when using streambank and near bank characteristics to predict relative erosion on sections of the same stream with different morphology and potentially different dominant erosional processes. When the streambank parameters were used to group sites independently of erosion, a group of streambanks with moderate rooting depths and densities, low bank angles, and surface protection emerged. This group experienced the least amount of erosion. Regression analysis showed that for noncohesive restored banks that were vulnerable to fluvial erosion, bank angle, bank height, and vegetation parameters were needed to predict susceptibility to erosion. Alternatively, for cohesive banks with non-cohesive bank toe material that were vulnerable to fluvial erosion and mass failure, bank angle, bank material, and near bank depth ratios with an emphasis on bank angle were sufficient parameters to predict susceptibility.

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