Modeling the Effect of Applied Shear Stress on Cohesive Riverbank Erosion

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Riverbank erosion, particularly of cohesive sediments, is of interest to many stakeholders within the Province of Manitoba. One only needs to think of the riverbank stability issues and subsequent property loss facing the City of Winnipeg each year to appreciate the significance of erosion. The Manitoba Hydro hydraulic system is also subject to these types of processes; its hydraulic system continuously experiences erosion and deposition of both cohesive and non-cohesive sediment. Current regulations for environmental impact statements require that project proponents address sediment transport processes, such as riverbank erosion, as well as any potential effect on aquatic systems. Unfortunately, the current state of knowledge of cohesive sediment transport is relatively limited, and there is no currently available numerical model or methodology that has been established and proven to be effective for predictions of cohesive sediment erosion. This project will endeavour to use years of monitored cross-sectional data from several Manitoba Hydro sites, detailed bathymetric and hydraulic monitoring of selected field locations as well as an erosion measurement device to provide data for developing a methodology for modeling the effect of applied shear stress on cohesive riverbank erosion. It is anticipated that a better understanding of these processes will assist Manitoba Hydro with the regulatory approvals process for future hydropower projects. Furthermore, existing sites within the Manitoba Hydro hydraulic system (ie. Nelson River, 8-mile and 2-mile channel, Winnipeg River) could benefit from a physically-based model to predict riverbank erosion. The methodology that is developed should be transferrable for use in studying other similar cohesive riverbanks within Canada.