University of Freiburg: Warning system for dangerous heavy rain and flash floods

In recent years, there have been repeated flash floods in Germany, some with devastating effects, which have been triggered by localized heavy rainfall. Up to now, it has often not been possible to warn of such events because their origins are complicated and they usually occur quickly and are spatially very limited. A new research project aims to close this gap in the warning system. It is coordinated by Prof. Dr. Markus Weiler, hydrologist at the Faculty of Environment and Natural Resources at the University of Freiburg. The Federal Ministry of Education and Research (BMBF) is funding the project, which will run for three years.

Scales from all of Germany down to the municipal level
The new research project is called AVOSS (which, in English, stands for Impact-based prediction of heavy rain events and flash floods at different scales: prospects, uncertainties and limitations). It is intended to provide prototypical warnings at different spatial scales, from the whole of Germany to individual federal states and down to the municipal level.

“Existing warning tools for heavy rainfall and its consequences only refer to the forecast of precipitation and disregard the current hydrological conditions,” explains Weiler. Hydrological properties, such as the current soil moisture and land cover, as well as the slope or soil properties, are ultimately decisive in determining whether a heavy rain event also triggers a flash flood. “A reliable flash flood warning system must therefore take hydrological factors into account in addition to meteorological ones,” says the Freiburg researcher.

Mapping hazards virtually in real time
Meteorological, hydrological and hydraulic information is to be linked in the project and combined to form a warning system that can depict the current risk of flash flooding virtually in real time. To this end, several universities and research institutions from all over Germany are working together with meteorologists and engineering offices in the interdisciplinary AVOSS project. In addition, practical stakeholders such as state authorities and municipalities are involved.

This is to ensure the practical suitability of the warning tools to be developed. Furthermore, prototype applications for pilot regions are planned to evaluate the quality and resilience of the flash flood warnings.