Disastrous flooding in July 2021 in Germany – Event analysis and consequences for risk assessment approaches

In July 2021 Germany has experienced devastating flooding with unprecedented impacts of around 180 fatalities and 30 billion € economic losses. To understand the main causes of this flood disaster, we analyze this event along the flood process chain, from the triggering atmospheric processes through catchment and river system processes to its impacts on people and the built environment. We discuss to which extent current approaches for flood mapping and risk assessment are able to provide sound information for preparing citizens, disaster management and administration against such events. We argue that risk assessments should be based on broader approaches that attempt to include a larger breadth of possible events, failure scenarios and impacts. Approaches, such as worst-case scenarios, downward counterfactuals, or historical storylines, and more comprehensive and refined impact modeling can substantially contribute to a better understanding of the potential for disasters.