Climate Change Impact on Flood Hazard in Europe: An Assessment Based on High-Resolution Climate Simulations

Global warming is generally expected to increase the magnitude and frequency of extreme precipitation events, which may lead to more intense and frequent river flooding. This work assesses the implications of climate change for future flood hazard in Europe. Regional climate simulations from the HIRHAM model with 12-km horizontal resolution were used to drive the hydrological model LISFLOOD at 5-km resolution. It was found that by the end of this century under the SRES A2 emissions scenario in many European rivers the extreme discharge levels may increase in magnitude and frequency. In several rivers, most notably in the west and parts of eastern Europe, the probability of what is currently a 100-year flood may double or increase even more, meaning that the return period decreases to 50 years or less. A notable exception to this was found in the northeast, where warmer winters and a shorter snow season reduce the magnitude of the spring snowmelt peak. Also in other rivers in central and southern Europe a considerable decrease in extreme river flows was found. The results were compared with those obtained with two HIRHAM experiments at 50-km resolution for the SRES A2 and B2 scenarios. Disagreements between the various model experiments indicate that the effect of the horizontal resolution of the regional climate model is comparable in magnitude to the greenhouse gas scenario. Also the choice of extreme value distribution to estimate discharge extremes influences the results, especially for events with a return period of more than 50 years.JRC.H.7-Land management and natural hazard