How can we simulate a landslide event

What happens when the flash flood comes

Heavy rain caused flooded streets in the municipality of Wenden in 2007.

Cooperation between the University of Siegen and the city's disposal company for flood protection in the city area started. The computer model is intended to help simulate flash floods and their consequences.

On August 28, 2002 it rained so heavily in Siegen that cellars and apartments were flooded and streets were flooded. The rains are so heavy that a landslide in the cemetery in Kaan-Marienborn washes coffins in front of the houses. A storm with dramatic consequences and major damage. Local flash floods like this one can hit any location equally. The Research Institute for Water and Environment (fwu) of the University of Siegen and the Waste Management Company of the City of Siegen (ESi) are now working in a cooperation project to research the dangers of heavy rain events for the city of Siegen. A computer model is intended to help simulate flash floods and their consequences - and thus take flood protection to a new level.

The project is called “Simulation of Heavy Precipitation in the City of Siegen” (SiSSi). The cooperation started at the beginning of 2016 and will run for four years. The cooperation agreement was signed by Ulrich Krüger (Operations Manager ESi) and Prof. Dr. Jürgen Jensen (Chair for Hydromechanics, Inland and Coastal Hydraulic Engineering) signed. “This is a lighthouse project - for the university and for the region,” says Prof. Jensen. “That should be the Siegen model. Hydraulic engineering is at home in Siegen, ”says Ulrich Krüger.

The university and city have been dealing with flood protection for years. “But what we are doing here goes one step further. We want to systematically record the precipitation event from rain to runoff, ”explains Prof. Jensen. Under the technical direction of Stephan Roth (ESi) and Dr. Jens Bender (fwu) are developing computer models with which the interaction between sewer and surface runoff can be simulated during heavy precipitation. Such a model could take into account various scenarios such as frozen ground in winter as well as punctual heavy rain and the consequences in the urban area.

“Water doesn't care how big the capacity of our canals is. What happens when everything is overloaded? By simulating the whole thing, we can find out where we can improve our measures, but where we also have to inform citizens about a risk and develop emergency plans, ”says Krüger. The first step is to identify those areas of the Siegen urban area that are at risk from flash floods.

On the basis of the results, maps of the danger of heavy rain should then be drawn up and protective measures developed. The disposal company supplies a large amount of data, for example, about the sewer network (630 kilometers), the rain inlets (16,000 pieces) and the measurements of the precipitation. A true-to-detail illustration of the urban area is to be created. "We want to develop a realistic model that reproduces nature and can simulate different situations," says Prof. Jensen. The data form the basis for a model that simulates what happens in Siegen when extremely heavy rain sets in. For example, what effects heavy rain would have on the industrial area in the Leimbachtal or the city center.

“It's also about creating awareness that this risk exists. Nature is more powerful than man. The better we prepare for which parts are at risk in the event of a disaster, the less the damage, ”says Prof. Jensen. This cooperation offers great potential for the University of Siegen. The research question was what data are needed to develop such a computer model. Furthermore, doctorates are to be prepared as part of the project.

Cooperation partners (from left): Kristina Fehler, Dr. Jens Bender, Prof. Dr. Jürgen Jensen (all University of Siegen), Ulrich Krüger and Stephan Roth (both waste disposal company Siegen).