System vulnerability and risk assessment of railway systems to flooding

Abstract. Floods have negative effects on the reliable operation of transportation systems. In China alone, floods cause an average of ~1125 hours of railway service disruptions per year. In this study, we present a simulation framework to analyse the system vulnerability and risk of the Chinese railway system to floods. To do so, we have developed a novel methodology for generating flood events at both the national and river basin scale. The resulting event set provides the basis for national- and provincial-level railway risk assessments, focusing in particular on affected trains, affected passengers and increased time for detoured trains. The results show that due to spatial variations in the railway topology and traffic flows, the system vulnerability of the Chinese railway system to floods in different basins is highly heterogeneous. Flood events in the Yangtze River Basin show the largest impact on the national railway system, with approximately 40 % of the national daily trains being affected by a 100-year flood event in that basin. At the national level, the average number of daily affected trains and passengers for the national system are approximately 200 trips and 165,000 people (2.7 % and 2.8 % of the total daily numbers of trips and passengers), respectively. In addition, the mean average increased time for detoured trains reaches approximately five hours. The event-based approach presented in this study shows how we can identify critical hotspots within a complex network, taking the first steps in developing climate-resilient infrastructure.