Impact of sediment transport formulations on breaching modelling

This paper analyses the ability of a classical shallow-water-Exner model to simulate the complex process of breaching of a non-cohesive earthen embankment, with a special focus on the sediment transport modelling. Two experimental test cases are presented: the overtopping of a sand embankment over its whole width, involving only vertical erosion, and a full three-dimensional (3D) breaching problem, with lateral erosion of the banks. Various sediment transport formulations are tested, including sheet-flow and classical bed-load, with and without accounting for a steep slope correction factor. It is shown that the steep slope correction does not play significant role in the simulated results. Variations are nevertheless observed in the results obtained with the different sediment transport formulations. These variations are amplified for the full breaching problem, where a local bank-failure operator is used. This highlights the importance of a good sediment transport modelling to accurately simulate a full breaching process.