The catastrophic flooding in July 2021 claimed the lives of more than 200 people in Germany and Belgium. The high death toll makes it clear that hazard mapping and risk communication must be improved as a matter of urgency. Researchers of the University of Potsdam, the Helmholtz Centre for Geosciences, the University of Louvain and the Johns Hopkins University analyzed the locations and specific circumstances of 224 deaths. Their findings show that many of these occurred outside the officially mapped flood hazard zones and that older people were particularly affected.
Heavy precipitation, caused by the low-pressure system “Bernd,” led to devastating floods in July 2021 across large parts of the German states of North Rhine-Westphalia and Rhineland-Palatinate, as well as in the Walloon Region of Belgium. In these three regions, 224 people died in the flash floods, more than half of them in the Ahrweiler county in Rhineland-Palatinate. To better understand the underlying causes, the researchers analyzed the individual circumstances of these documented deaths using official records, media reports, and interviews with family members.
The results reveal that the areas actually flooded in 2021 differed significantly from the officially mapped flood hazard zones. Of the 224 locations where the victims died or were found, in North Rhine-Westphalia about 50 percent, in Rhineland-Palatinate even 75 percent were located outside the mapped hazard zone of an extreme flood scenario. “Consequently, the available flood hazard maps were not sufficient to adequately illustrate the risks to the public,” says lead author Prof. Annegret Thieken of the Institute of Environmental Science and Geography, University of Potsdam. To improve their accuracy, it is imperative to take historical floods into account or to estimate the worst-case flood scenario and display it on the maps.
In North Rhine-Westphalia, 14 people died while trying to reduce the damage, check pumps or start cleanup in basements. “This points toward deficiencies in communicating safe behavior during flooding,” stresses Annegret Thieken. In the three regions studied, a total of 81 people died on the ground and upper floors of their homes; many circumstances suggest that they were caught by surprise by the floodwaters. These buildings should have been evacuated in time, because staying outdoors in a flooded zone is even more dangerous. Deaths resulting from flooded or collapsed bridges, as well as vehicles that were swept away or stranded, are evidence of this.
The authors recommend that risk and crisis communication should clearly distinguish damage‐reducing and life‐saving behaviors. “Warning messages must clearly and timely communicate when evacuation from flood‐prone areas is still possible, and when it is no longer advisable,” she says. In the latter case, vertical self‐evacuation, i.e., going upstairs, should be recommended.
The findings also reveal a lack of strategies to care for vulnerable groups. In all three areas, people over the age of 60 were significantly overrepresented among flood victims, accounting for 72 percent. In Rhineland-Palatinate, twelve people died in a flooded residential home for adults with mental disabilities. “In general, the circumstances of many fatalities in July 2021 demonstrate that evacuation strategies need more attention, especially in order to better protect the older population, people with mobility impairments or preconditions,” says Annegret Thieken. “Therefore, we call for a revision of the European Floods Directive to better address worst‐case scenarios in hazard mapping, risk management, and communication.”
Link to Publication: Thieken, A. H., Rhein, B., Hosten, E., Zenker, M.‐L., Merz, B., Bubeck, P., et al. (2026). Understanding flood fatalities: Reevaluating flood risk management. Earth's Future, 14 , e2026EF008695. https://doi.org/10.1029/2026EF008695
Image: Destroyed bridge in the Ahr Valley after the catastrophic flooding in July 2021. Photo: AdobeStock.
Contact:
Prof. Dr. Annegret Thieken, Institut für Umweltwissenschaften und Geographie
Tel.: +49 331 977-2984
E-Mail: annegret.thieken@uni-potsdam.de
Media Information 04-09-2026 / Nr. 074
Dr. Stefanie Mikulla
University of Potsdam
Press and Public Relations Office
Am Neuen Palais 10
14469 Potsdam
Tel.: +49 331/977-1474
Fax: +49 331/977-1130
Email: presse@uni-potsdam.de
Website: www.uni-potsdam.de/presse
Earth's Future
Understanding flood fatalities: Reevaluating flood risk management
3-Sep-2026