A GIS-Based Flooding Indicator for Heavy Rainfall Hazards Along the German Railway Network: Case Study Nordrhein-Westfalen

Climate-induced natural hazards can result in disruptions and failures of railway routes which are associated with high economic costs. Hence, the mechanisms of climate impacts posing a threat to rail transport must be identified, analysed and localised in railway networks. This study aims at assessing heavy rainfall hazards on the railway network of the federal state Nordrhein-Westfalen (NRW) in Germany and presents a GIS-based flooding indicator. A rule-based classification and aggregation approach with a hazard matrix was developed using potential flooding depths and flow velocities, resulting in five hazard classes. The approach was applied to the railway network in NRW for two heavy rainfall scenarios (N100, Next). The results show that the clear majority of route kilometres are classified as at least moderate hazard in both precipitation scenarios considered (Next 81%, N100 72%). On railway routes in low mountain range regions, more sections are assigned higher hazard classes than in flat landscapes. The plausibility of the indicator was explored through scenario, structural and conceptual parameter analyses, which support robustness of the results. The maps can serve as a tool for making qualitative statements on the potential impact on the German railway network and localising these impacts spatially.