Projections of river floods in Europe using EURO-CORDEX, CMIP5 and CMIP6 simulations

A large ensemble of hydroclimatic simulations is used to simulate the occurrence of river floods over Europe in a climate change context. A river routing model derived from a distributed hydrological model (CHyM) is forced with 44 EURO-CORDEX, 13 CMIP5 and 7 CMIP6 simulations to assess the effects of climate change on the flood magnitude under two different scenarios. The impact of climate change is evaluated using a 100-year return period discharge indicator (Q100). Results show a decrease in magnitude of Q100 flood events over the Mediterranean, Scandinavia and north eastern Europe. This latter signal appears particularly robust and in contrast to the projected mean flow signal, which is shown to increase by the end of the century in response to increased mean precipitation. The reduction of snow accumulation during winter induced by a large increase of late winter temperatures is the main reason behind the decrease of floods over the North Eastern regions. An opposite signal is projected over Great Britain, Ireland, Northern Italy and Western Europe, where a robust signal of flood magnitude increase is evident, being driven by an increase of extreme precipitation events. All these simulations are intended for use in impact assessment studies towards the development of suitable response options.