Unsteady numerical modeling of river hydraulics and morphology changes

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Sediment transport modelling is widely used in fluvial hydraulics, such as for the assessment of the determination of risk areas downstream of a dam. Existing sediment transport relationships assume steady state hydraulics. In many practical situations, in which sediment movement is likely, the hydraulic state is very unsteady. Flow unsteadiness introduces dynamic effects not accounted for by existing "steady flow" relationships which can have dramatic effects such as the catastrophic effect of Hurricane Katrina on New Orleans, the Red River Flood of 1997 along the Red River in North Dakota, Minnesota, and Southern Manitoba and the downpours of the Saguenay in 1996. Moreover, only some local stream restoration actions take place after such floods: local bank stabilization, local sediment removal.... Any attempt to recreate a self-sustaining natural system requires an understanding of the geomorphic processes that characterize a certain river and how these processes can be supported by present (or future) flow regimes. Our goal is to develop an integrated stream-riparian corridor approach to be used in conjunction with watershed-scale analysis, for evaluating the long-term effectiveness of proposed corridor rehabilitation designs. This new approach is a critical need for hydraulic engineers, fluvial geomorphologists, landscape architects, and stream ecologists involved in stream rehabilitation projects. These projects are usually challenged by the lack of integrated design tools to evaluate the long-term stability of reconstructed stream corridors.