Using numerical models to estimate the impact of run-of-river dams on bed load transport processes and channel bed evolution in British Columbia

Using a 1-D morphodynamic model as our primary tool, we are investigating the potential impact of run-of-river dams on sediment transport processes and channel bed evolution. The model is used to predict the grain size distribution of sediment exposed at the surface and in transport as well as the bulk transport rate. The model can predict these quantities as a function of space and time in response to dam closure. Initially the model will be applied to the reach downstream of the powerhouse where the channel hydrology is largely unaltered.Given the geomorphic variability of run-of-river sites in British Columbia, and the variability in operating procedures among the sites, we will model several different sediment supply reduction scenarios (e.g. temporary reduction, sediment pulse scenarios, total elimination). In order to ground the model in reality, we will use field data collected from proposed project sites in British Columbia as inputs to the numerical model. Our goal is to provide general predictions that can be used to estimate long-term cumulative impacts of run-of-river projects on channel morphology and channel bed characteristics. Ultimately, our model predictions will be incorporated into a decision support tool designed to help minimize trade-offs between the economics of project development and the sustainability of aquatic ecosystems in British Columbia