Gekoppelte 1D-2D hydraulische Modellierung urbaner Sturzfluten – RAINMAN-Pilotstudie Graz Eggenberg

Over the last decades an increase in urban flash floods due to heavy storm events can be observed. This leads to significant risks and damage to housing and infrastructure. In scope of the RAINMAN project, pilot studies were conducted for several catchments using an integrated 1D-2D hydraulic model. This contribution discusses model sensitivity based on two major parameters and rainfall distribution and shows the impacts of the coupled model for one pilot study catchment in the City of Graz, Austria. Results show that relatively small changes in the parameter values can lead to significant changes in the resulting peak discharge and runoff volume. Also, the chosen rainfall distribution for the synthetic storm events shows a relevant impact on the results. As data for model calibration can be expected to be rarely available for similar catchments, we advocate to conduct a sensitivity analysis and to validate the results against empirical runoff values and practical experiences from local stakeholders—especially as the results have impact on risk assessment and potential protection measures. Model coupling of surface flow and sewer system shows locally significant impacts for the pilot catchment. Possible interactions of the system should therefore be considered in an urban context.