The project in cooperation with the city of Kaiserslautern with respect to the flooding of the Erlenbach district in May 2000 represents a typical application of the software developed within the main subject Flood and Risk Management.

A heavy rainfall of the order of magnitude 70 mm per hour, fallen on the watershed of Illerbach and Ellerbach, which has an approximate size of one square kilometer, resulted in a massive flooding of the district of Erlenbach. The objective of the project is the determination of the flow processes of that event and the estimation of the flooding risk for the district by simulations of the run-off behavior after model rainfalls of given return periods. On the basis of the results, building measures are to be examined also based on simulations with respect to their capacity of decreasing the number of flooding risk.

In the simulation, simplified shallow water equations are solved for the computation of water levels at the surface depending on space and time. The model representation includes the topography and surface parameters, such as permeabilities and roughnesses. All the necessary data are extracted by the GIS and positioned on a triangular grid of adaptive cell size. Large model areas with only smoothly varying parameter distributions, as they occur in the domain of the natural watershed, are to be combined with model details to be determined exactly, such as streets and brooks, as well as with the slope separating the urban area from its watershed. The urban area is located at the back and can only be flooded by water from the watershed if the sewer inlets at the bottom of the slope are closed or if their capacity is exceeded, so that the basin in front of the slope cannot cope with the in. owing masses of water any longer.  

The simulation of the run-off processes in the case of the heavy rainfall of May 2000 shows that the mentioned flooding case occurs although the channel inlets are open. We can conclude that, in the case of rainfalls of the intensity observed at that time, there is a high risk potential for the district due to inconvenient run-off conditions. Rainfalls of a 50 year return period will probably cause flooding. Different relief measures can now be dimensioned and tested after their implementation into the computer model.

• Simulation (animation in MPG)