Inundation of a Dutch river polder, sensitivity analysis of a physically based inundation model using historic data

The inundation model Delft flooding system (Delft‐FLS) was applied to simulating the historical flood of 1805 in the polder Land van Maas en Waal (Netherlands). Delft‐FLS is a two‐dimensional (2‐D) hydrodynamic model that simulates overland flow. Sensitivity analyses show a large influence of floodplain topography and hydraulic friction on the propagation of the inundation. Because of the typical topography of Dutch polders, a virtually flat floodplain bordered by high dikes, the extent of the inundated area alone cannot be used for evaluating the model performance. Therefore the inundation time and water levels within the inundated area were used to test the model capabilities. This study shows that using historic data has a potential advantage over using contemporary data. Historic data allow evaluation of a model for real flood disasters that have long return periods and, fortunately, have not occurred in modern times.