Continuous, large-scale simulation model for flood risk assessments: proof-of-concept

In this paper we present the Regional Flood Model (RFM), a process-based model cascade developed for large-scale basins. The objective of this study is to demonstrate that flood risk assessments, based on a continuous simulation approach, including rainfall-runoff, 1D river network, 2D hinterland inundation and damage estimation models, are feasible at the scale of large catchments. RFM is applied to the German part of the Elbe catchment including around 2700 river-km. For this proof-of-concept study, simulations are performed continuously over the period of 1990-2003. Simplification of equations and parallelisation enable the continuous 2D hydrodynamic inundation simulation with reasonable run-times on a relatively high resolution of 100m. As uncertainties are introduced with each module along the model chain, results are evaluated, where possible, with observed data. Results indicate that uncertainties are significant, especially for hydrodynamic simulations. This is basically a consequence of low data quality and disregarding dike breach effects in the simulations. Reliable information on overbank cross-sections and dikes is expected to considerably improve the results. We conclude that the large-scale simulation of catchment processes, inundation and damage, driven by long-term climate data, is viable within a continuous simulation framework. It has the potential to provide a spatially consistent, large-scale picture of flood risk.