Submitted to: Geomorphology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2008
Publication Date: 7/2/2008
Citation: Parker, C., Simon, A., Thorne, C. 2008. The Effects of Variability in Bank-Material Properties on Riverbank Stability: Goodwin Creek, Mississippi. Geomorphology, doi:10.1016/j.geomorph.2008.02.007. Interpretive Summary: Streambank erosion is a major source of sediment to the nation’s rivers. Tools to prediction erosion rates and sediment loadings from bank erosion have been developed by the National Sedimentation Laboratory. Uncertainty in predictions, however, can be caused by variability in the input values that are assigned to the strength of the bank materials. This occurs because fine-grained soil materials can have variable characteristics over short distances. This source of uncertainty in the bank-stability and toe-erosion model is investigated in this paper where bank failure is predicted if the factor of safety falls below 1.0. Results show that considerable variation in the measured strength of bank materials can have an important influence on predictions of bank failure and because of this, and approach that relies on the probability of failure is suggested over one that provides only a single factor of safety value.
Technical Abstract: Bank erosion is an important area of research within fluvial geomorphology and is a land management problem of global significance. The Yazoo River Basin in Mississippi is one example of a system which is a victim of excessive erosion and bank instability. The properties of bank materials are important in controlling the stability of stream banks and past studies have found that these properties are often variable spatially. Through an investigation of bank material properties on a stretch of Goodwin Creek in the Yazoo Basin, Mississippi, this study focuses on: i) how and why effective bank material properties vary through different scales; ii) how this variation impacts on the outputs from a bank stability model; and iii) how best to appropriately represent this variability within a bank stability model. The study demonstrates the importance that the variability of effective bank material properties has on bank stability: at both the micro-scale within a site, and at the meso-scale between sites in a reach. This variability was shown to have important implications for the usage of the Bank-Stability and Toe-Erosion Model (BSTEM), a deterministic bank stability model that currently uses a single value to describe each bank material property. As a result, a probabilistic representation of effective bank material strength parameters is recommended as a potential solution for any bank stability model that wishes to account for the important influence of the inherent variability of soil properties.