ABSTRACT
This paper proposes an analysis of the limitations of the low-slope assumption in the shallow water models for problems involving rather steep slopes. First, the equations including the steep slope effect are presented in one dimension and compared to the classical shallow-water equations. Both models are solved with a first-order classical finite volume scheme. The models give comparable results when compared on fast transient flows on steep slopes, while they differ when modelling uniform steady flows. They also lead to comparable results in the particular case of a flow overtopping a dike. Finally, the impact of the classical shallow water assumptions on the sediment transport evaluation is analysed. Comparable conclusions are drawn for sediment transport modelling, showing that the classical shallow water model is suitable for fast transient flows, but more accurate models should be used when modelling erosion for steady uniform flows.
