Flash Floods - Run-off Generation Research Model (RoGeR)

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:

• HOF Horton overland flow
• SOF saturation overland flow
• MPI macropore interflow
• DP deep percolation

and using adequate run-off concentration concepts:

• Run-off depths or percentage of total flow (area specific)
• flood water volume (catchment or part of basin)
• flood wave at a virtual gauging station for arbitrary regions.

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.

References

• A. Steinbrich, M. Weiler: Ausweisung der für die Hochwasserentstehung wichtigen Abflussbildungsprozesse für Baden-Württemberg Niederschlag-Abfluss-Workshop, 2010
• A. Steinbrich, M. Weiler: A non-calibrated, runoff process-based rainfall-runoff model for prediction of floods in ungauged basins EGU General Assembly 2010, 2010; Geophysical Research Abstracts 12, EGU2010-6668
• S. Uhlenbrook, A. Steinbrich, D. Tetzlaff, Ch. Leibundgut: Zusammenhang zwischen extremen Hochwassern und ihren Einflussgrößen KLIWA Symposium, 2001: 187-204