Hydrodynamic levee-breach and inundation modeling of a levee district along the Middle Mississippi

Computer-based levee breach and inundation simulations are presented for a levee district along the eastern shore of the Middle Mississippi River. The different simulated scenarios include flooding of the district starting from a northern, a western and a southern levee breach. In the study, a hybrid 1D2D flow model was used that combines a 1D model of the Mississippi River with a 2D overland flow model of the levee district. The development of the levee breach is based on an empirical dam break formulation that calculates dimensions of the breach opening from flow characteristics in the breach and the erodibility of the levee. Next, using different floodplain roughness maps a sensitivity analysis is carried out of the simulated flood events, highlighting the impact of floodplain land cover on maximum breach size, flood arrival times and maximum inundation depths. Also, a classification scheme is proposed that characterizes different flood phases. Each flood phase is associated with particular flow conditions and thus requires different types of flood mitigation strategies.