Rainstorm Flood Risk Assessment of Urban Metro System in Different Operating Periods: A Case Study of the Central Urban Area of Tianjin, China

The rapid expansion of China’s Urban Metro System (UMS) corresponds with the burgeoning growth of urban areas driven by the country’s swift urbanization. In the context of escalating extreme rainstorm events linked to global climate change, the UMS confront a growing risk of flood inundation. Using the central urban area of Tianjin as an example, the Infoworks ICM hydrological model was utilized to simulate inundation extents and depths in the study area for four selected rainstorm return periods. Furthermore, the vulnerability of the metro stations was assessed by utilizing analytical hierarchy process-technique for order preference by similarity to ideal solution (AHP-Topsis) and constructing a multi-indicator system. The study employed the H-E-V risk assessment framework for the quantification of rainstorm flood risk. The findings reveal noteworthy insights. (1) The variations in the metro operating periods can significantly impact the rainstorm flood risk of the UMS, and the number of higher and highest risk metro stations is greater during rush hours than during offpeak hours. (2) The installation of exit steps emerges as a feasible measure to mitigate the potential impact of rainstorm floods on the UMS. (3) In addition to being in the central area of the case zone, highest risk metro stations are also distributed around the periphery of the study area.