One-dimensional modeling of the flows and morphological changes in rivers : experimental and numerical approaches

Floods are highly damaging natural disasters and their impact is often increased by the transported sediments. To minimize material damage and human life loss, reliable prediction of these floods are necessary. The present thesis aims at modeling fast transient free-surface flows and morphological changes consecutive to dam or dike failures using 1D models. This work is divided in two parts: hydrodynamic flow and morphological changes. In the hydrodynamic part, three aspects are studied. First, source terms computation and discharge conservation are investigated comparing the results of three approaches. Secondly, flows around islands are considered. To include this 2D phenomenon where the river is divided in two sub-channels on each side of the island, internal boundary conditions are used, considering characteristic paths and energy conservation. Finally, a non-intrusive photogrammetry technique is presented to measure the water level on a wide area of the flow in laboratory experiments, allowing the production of detailed an accurate validation data for the numerical models. The morphological changes part starts with the comparison of four different approaches. These differ in the fluxes computation and the level of coupling between sediment and water flow equations. Then, dike breaching experimental data are compared to 1D and 2D models predictions. The breaching presents some 2D features such as the breach widening but the adapted 1D model provided surprisingly good results. Finally, experiments of scouring at the interface between fixed and mobile bed in steep sloped channels have been conducted, where different phases in the flow have been highlighted as well as the relations between velocity fields and scouring.