Due to exceptional rainfall intensities and quantities (150 - 270 mm in 48 hrs) between 13 and 15 July 2021, the area between Liège (eastern part of Belgium), Maastricht (southern part of the Netherlands) and Köln (mid western part of Germany) had to deal with an unprecented flooding disaster. In total, more than 220 persons lost their lives and estimates of the insured losses mount up to €2.55 billion, with the total damage costs being much higher. The return-period of the observed precipation scenarios is estimated between 30 to 100 years.
Due to climate change it is expected that the occurence frequency of such extreme precipitation events increases. In addition, the older series of precipitation measurements cover about 300 years, meaning that we did not yet observe many of those extreme events. Therefore, although robust climate change signals are detected for future seasonal and multi-day extremes, uncertainty in our current extreme value statistics still need to be taken into account wenn preparing our natural hazard management strategy for the future. Thinking the unthinkable will have to be one part of it, meaning that we also will have to simulate and assess the impacts of events which we did not observe until now.
