River modelling and flood mitigation in a Belgian catchment

This paper describes the steps followed to propose solutions to recurring flooding problems in a Belgian catchment. First, the hydraulic capacity (maximum discharge before bank overflow) of the cross-sections was computed along the entire river by an iterative one-dimensional steady-state approach. In order to carry out these simulations, cross-sections from site surveys of the river were integrated into the model, as well as hydraulic structures such as culverts, footbridges and pipes. Second, the flooding problem was analysed with a time-dependent approach consisting of simulating floods following extreme rainfall events. The hydrological aspect was studied in a spatially distributed way using a multi-layer hydrological model. The available data on the basin such as the digital elevation model, the land-use and the pedology were exploited to identify the basic modelling parameters. The hydrological contribution was routed by a one-dimensional network resulting from the merging of the digital elevation model-based and the cross-section-based river networks. According to the results of the aforementioned steps, various local and catchment-wide solutions against flooding were proposed and analysed. The comparison of simulated situations before and after these improvements allowed the effectiveness of the proposed solutions to be checked.