Transboundary hydraulic modelling of extreme floods in the Meuse River

Detailed inundation modelling was conducted along a 100 km long transnational section of the Meuse River (in Belgium and The Netherlands), using very similar models for the whole computation (2D unsteady models). As a result, damping of the flood waves could be quantified and the possible relevance of using a steady-state approach could be assessed. The new detailed 2D hydraulic simulations have demonstrated that only a very limited damping of the flood waves occurs along the simulated reaches. From the perspective of the variation in peak discharge, the study concludes that running the hydraulic model in steady mode makes perfectly sense. Nonetheless, the steady computations lead to extensive overestimations of the inundated extent and of the stored volume in the floodplains. The 2D unsteady model constitutes also a tool of primary interest, which is readily available to design and evaluate protection measures for flood-prone areas such as in the city of Liege.