Comparison of three methods assessing the inundation caused by the erosion of an embankment

Abstract

Two test cases of embankment breaching are selected in order to compare a simplified model to 2-D calculations. The simplified model is based on an erosion model of the levee completed by the calculation of the head available between upstream and downstream sides of the embankment and two empirical models for wave propagation. The 2-D model is based on shallow water equations; it can be completed either by the same breach erosion model as in the simplified model or by an equation of sediment transport. The first test case is an experiment in Norway in which the embankment closes the valley. This latter example shows that all the models agree between them and differ from the experimental results because of the uncertainty of the input data and of the measurements. 2-D modelling does not bring any advantage except if sediment transport is simulated on a refined grid in order to obtain the detailed topography at any time. The second case is a breaching of a levee protecting the flood plain during high flows in Agly River. The difficulty stands in providing the hydraulic conditions in the river upstream from the breach and in propagating the flood wave in the complex topography of the flood plain. In such a case, the 2-D model that permits to test various assumptions and link them with physical processes can more easily provide an estimate of the uncertainty of the results