Future projections of river floods over the European region using EURO-CORDEX simulations

In a sick world with fever caused by global warming, the hydrological cycle will experience most certainly large changes in intensity and variability. One of the most intense phenomena that will probably be affected by the climate change is the flood hazard. For a long time the stakeholders have been dedicated resources to assess the risk linked to the floods magnitude and frequencies and shaping the public infrastructures based on the assumption of their immutability. Under the effect of the climate change this assumption can be broken and a different approach should be followed to avoid large disasters and threaten to the population health. In this study the biggest ever ensemble of hydroclimatic  simulations has been used to simulate the river floods over the European regions. A river routing model derived from a distributed hydrological model (CHyM) has been forced with 44 EURO-CORDEX, 5 CMIP5 and 7 CMIP6 simulations to assess the effects of the climate change on the floods magnitude under two different scenarios (RCP2.6 and RCP8.5 for EURO-CORDEX and CMIP5, SSP126 and SSP585 for CMIP6). The impact of the climate change has been evaluated using a 100 year return period discharge indicator (Q100) obtained fitting a Gumbel distribution on the yearly peak discharge values. Results show a decrease of magnitude of flood events over the Mediterranean, Scandinavia and the North Eastern European regions. Over these two last regions the signal appear particularly robust and in contrast to the projected mean flow signal that is shown to increase by the end of the century mainly driven by the related increase of mean precipitations. The reduction of snow accumulation during winter time linked to 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  instead over Great Britain, Ireland, Northern Italy and Western Europe where a robust signal of floods magnitude increase is evident driven by e the increase of extreme precipitations. All these simulation are meant to feed the impact community and to shade the light on the use of climate information for impact assessment studies.