Author(s): F. Franzini; S. Soares-Frazao
Linked Author(s): Sandra Soares-Frazao
Keywords: River hydraulics; Sediment transport; Fast transient flows; Numerical modeling; Morphodynamics
Abstract: The major flood following the Lake Ha! Ha! dyke-break in 1996 in Quebec (Canada) induced important morphological changes in the valley. For instance, massive erosion was witnessed along with significant valley enlargements. Another interesting observation was the creation of an avulsion, i. e. a new river bed. Due to the very complex and irregular topography of the valley, flow simulations in that area constitute a real challenge for numerical models. Indeed, the river presents very steep slopes at some locations, or very abrupt changes in cross-section shape. The presence of rocky outcrops creates another difficulty because of its impact on the erosion process. The focus of the research is to simulate the Lake Ha! Ha! dyke-break event using a onedimensional finite-volume scheme solving the Saint-Venant-Exner equations in a decoupled way. First, the analysis is conducted from the pure hydrodynamical point of view allowing the characteristics of the flow to be computed. Then, these characteristics are used to determine the sediment transport and, finally, the morphological changes. Even though the model uses a onedimensional framework, bank erosion and bank failure processes are also accounted for. Comparisons between the computed final topography and field measurements are provided, along with a discussion about the quality of the results and the key issues for future research.