Simulation of future extreme rainfall events over Belgium with a focus on the Vesdre valley using the regional climate model MAR.

The rainfall in July 2021 that hit West Germany, Netherlands and Belgium was of unprecedented intensity. To assess the probability of such events ocuring in a near and far future (until 2100), the regional climate model MAR has been used to make simulations at a resolution of 7,5 km. To this end, the regional climate model MAR is linked to a set of Earth System models (ESMs) with 4 IPCC SSP scenarios over a domain that includes Belgium and Luxemburg. The analysis focused on the valley of the Vesdre which in Belgium was the most impacted by flooding in terms of damage to human infrastructures.

For some specific climatic conditions, MAR simulates events of similar intensity to those of the 2021-floods over the next 5 decades. To assess the statistic significance of the results, a Peaks Over Threshold analysis (POT) has been applied to MAR outputs for precipitation events of 1,2,3,4 and 5-days. Quantiles associated with high return periods have been calculated for the historical period of simulation (1980-2010) and for the 2011-2040, 2041-2070 an 2071-2100 periods. This shows that the frequency of such events in the periods 2011-2040 and 2041-2070 is likely to increase if climatic conditions are wet enough. For global warming levels above 3 to 4 °C, conditions appear too dry for such events to occur.