Predicting the flow in the floodplains with evolving land occupations during extreme flood events

The flood hazard must be accurately assessed in high-risk areas during extreme flood events. However, the prediction of the very high flows is not an easy task due to the lack of field data and to the strong link between flow resistance and the land occupation of the floodplain. With increasing return period T, the confinement and the inhomogeneity in lateral and longitudinal directions of the hydraulic roughness elements strongly vary. The physical processes are complex, still largely unexplored, and the assumptions linked to numerical modeling cannot be validated without field data. The project aims at improving the flood hazard assessment in floodplains in: 1) investigating in laboratory the hydrodynamic structure associated with extreme flood flows for various land occupations and flow discharge magnitudes; 2) assessing if the existing numerical modeling practices used for T ~ 100 years are still valid for T > 1000 years, relying on the experimental data and on one field case (floods at Besançon, France)