Flash flood risk assessment for the German federal trunk road network

Abstract

n recent years, heavy rainfall events have frequently affected transport infrastructure in Germany. According to various climate projections, an increase in heavy rainfall events is expected. The project “Local analysis and mapping of potential flood areas in the federal trunk road network of North Rhine-Westphalia as a result of heavy rainfall events (Blue-Spot-Analysis)” has been initiated by the Federal Highway Research Institute (BASt). The project aims the development of a hydrological and hydraulic modelling and GIS analysis toolset approach that identifies potential flash flood hazard and risk on national trunk roads. The method has been developed and tested for one federal state with the goal to conduct a flash flood hazard and risk assessment on a national scale in future. Using a hydrological-hydraulic model cascade, potential flash flood areas has been mapped on the basis of a 2D-hydrodynamic raster model. The resulting inundation depths and flow velocities show potentially flooded areas for different rainfall intensities. A detailed risk analysis conducts the major “blue spots” restricting functionalities on the trunk road system. The derived maps contribute significantly to the development of adaptation strategies to protect the federal trunk road network against local flooding caused by heavy rainfall events.