For the City of Düsseldorf, there is not only a need to protect the urban area from flooding from the river Rhine, but also from flooding from the smaller tributaries on the right bank of the Rhine, including the eponymous Düssel river. The Düsseldorf geoportal, called „Düsseldorf Maps“, provides our citizens with information to eventually take precautions. There are not only the flood hazard maps of the NRW state government, but also forecast maps for heavy rain floodings and maps with infiltration potentials to support preventive measures. However, these forecasting methods are based on statistical parameters and are less useful in acute situations. Due to the short flow distance of the tributaries and the topographically low mountain situation of the upper reaches, the warning time for flooding is extremely short. To extend the advance warning times, the City of Düsseldorf, in cooperation with the Kreis (district) Mettmann and the Bergisch-Rheinischer Wasserverband, is developing a flood forecasting tool that evaluates water level parameters, current and expected precipitation and soil moisture in order to display flood hydrographs and maps of expected flooding area online.