Intense rain and resulting flash floods often result in serious damage which amount to similar figures compared with flood destruction along rivers (URBAS, 2008). Such events can occur nearly everywhere - in settled areas as well as in the countryside with land uses from forest to grassland or arable land, the last one is often prone to erosion. Flash floods are often a consequence of heavy (local) convective shower precipitation. They cause damage in settled areas by overloading the sewage water system and uncontrolled run-off along streets or other preferred pathways.
In the context of the Federal State project of water and soil atlas of Baden-Württemberg (WaBoA), the model RoGeR has been established at the Institute of Hydrology at the University of Freiburg. This GIS-based precipitation run-off model calculates in the highest spatial resolution on a 1*1 m grid in a process-oriented way and allows quantifying the run-off components or the sum of the fast run-off components respectively:
and using adequate run-off concentration concepts:
There is no calibration of the model and the run-off coefficient is evaluated dynamically in dependence of precipitation development and soil water storage. Scenarios
can therefore quantify the run-off generation following rainfall using weather radar precipitation data, for example, in an area-detailed way with time resolution from minutes to hours.
According to the literature, (e.g. climate status report (Klimatatusbericht, 2002)), the number as well as the intensity of heavy rain and the percentage of rain falling as heavy rain is expected to rise in Central Europe. Consequently, the issue of flash floods will arise, even when present work in the context of a flood water management directive in Germany does not show priority on the issue.