Occurrence and Characteristics of Flash Floods in Bavaria (Germany)

Due to the global warming, an increase in the number and intensity of flash flood events triggered by heavy rain is expected. Flash flood risk management requires the identification of regions where the occurrence of flash flood events can be expected to become more frequent. In this study, we shed light on the occurrence and characteristics of flash floods in the state of Bavaria, Germany. A discharge time series of 342 gauging stations (average measurement period 1960–2017) was investigated with regard to the past flash flood events. The catchments of the selected gauging sites range from 1 to 500 km² and are not affected by flood retention structures. Only half of the chosen gauging stations recorded flood events, which showed a short response time and a significant flood magnitude that were typical for flash floods. This led us to the conclusion that some catchments are more prone to flash floods than others. It was found that the flash flood occurrences are not evenly distributed over Bavaria, but rather form spatial clusters in the alpine region and the Bavarian Forest. The statistical evaluation of 5,732 flash flood hydrographs for different catchment sizes further deepened our understanding of the characteristics of this natural hazard in Bavaria.