Assessment of future flood hazard in Europe using a large ensemble of bias‐corrected regional climate simulations

Abstract

We assess future flood hazard in view of climate change at pan‐European scale using a large ensemble of climate projections. The ensemble consists of simulations from 12 climate experiments conducted within the ENSEMBLES project, forced by the SRES A1B emission scenario for the period 1961–2100. Prior to driving the hydrological model LISFLOOD, climate simulations are corrected for bias in precipitation and temperature using a Quantile Mapping (QM) method. For time slices of 30 years, a Gumbel distribution is fitted by the maximum likelihood method through the simulated annual maximum discharges. Changes in extreme river flows, here exemplified by the 100‐year discharge (Q100), are then analyzed with respect to a control period (1961–1990). We assess the uncertainty arising from using alternative climate experiments to force LISFLOOD and from the fitting of extreme value distributions. Results show large discrepancies in the magnitude of change in Q100among the hydrological simulations for different climate experiments, with some regions even showing an opposite signal of change. Due to the low signal‐to‐noise ratio in some areas the projected changes showed not all to be statistically significant. Despite this, western Europe, the British Isles and northern Italy show a robust increase in future flood hazard, mainly due to a pronounced increase in extreme rainfall. A decrease inQ100, on the other hand, is projected in eastern Germany, Poland, southern Sweden and, to a lesser extent, the Baltic countries. In these areas, the signal is dominated by the strong reduction in snowmelt induced floods, which offsets the increase in average and extreme precipitation.