Deriving strong rain hazard risk maps from geo-morphology

Kurzfassung

In the last summer a long time stationary rain event struck parts of western Germany leading to massive floodings especially in the Ahr valley. Such long-term stationary weather conditions get actually more and more frequent and can lead to long extreme heat or massive continuous rainfall as shown in a study of the Potsdam-Institut für Klimafolgenforschung (PIK) last year (Rousi, E., Selten, F., Rahmstorf, S., Coumou, D. (2021): Changes in North Atlantic atmospheric circulation in a warmer climate favor winter flooding and summer drought over Europe. Journal of Climate, 34, 6, 2277-2295. https://doi.org/10.1175/JCLI-D-20-0311.1 ). The flood of the Ahr revealed that the existing modelling for flood probabilities is not sufficient. Possible causes may be the comparatively short observation period of the underlying measurements, missing historical data or the dynamics of climate change are not taken into account. For this reason, our approach is based on simulations of individually adapted worst case scenarios to derive possible effects of heavy rainfall more generally and over a wide area just based on satellite data and digital elevation models. So its a simplified model which can be adapted and applied fast to regions all over the world - especially regions with only sparse available data.