Scenario-based inundation analysis of metro systems: a case study in Shanghai

Abstract

Abstract. Catastrophic urban floods result in severe inundation of underground facilities in recent years. This paper presents an integrated approach in which an algorithm is proposed to integrate the storm water management model (SWMM) into the geographical information system (GIS) to evaluate the inundation risk. The proposed algorithm simulates the flood inundation of overland flow and metro station for each schemed scenario. It involves i) determination of the grid location and spreading coefficient and ii) iterative calculation of the spreading process. Furthermore, to evaluate the potential inundation risks of metro systems, an equation to qualitatively calculate the inundation depth around a metro station is proposed. This equation considered the drainage capacity and characteristics of each metro station. The proposed method is applied to simulate the inundation risks of the metro system in the urban centre of Shanghai under 50-year, 100-year, and 500-year scenarios. Both the inundation extent and depth are derived. The proposed method is validated by verifying from the records of historical floods. The results demonstrate that in case of the 500-year-rainfall scenario, for an inundation depth of over 300 mm, the inundated area is up to 5.16 km2, which is 4.3 % of the studied area and that there are four metro stations inundated to a depth of over 300 mm.