Flood risk assessment of metro stations based on the SMAA-2-FFS-H method: a case study of the “7 · 20” rainstorm in Zhengzhou, China

Motivated by the realistic demand of reducing the flood risk of urban metro stations, this paper proposes an innovative research framework for flood risk assessment and classification. In this framework, a specified criterion system is established from the perspective of hazard, vulnerability, exposure and rescue capacity. Furthermore, we introduce an application of the SMAA-2-FFS-H approach to verify the practicality and efficiency of the proposed framework. As an extension of SMAA-FFS-H proposed by predecessors, the SMAA-2-FFS-H method comprises stochastic multi-criteria acceptability analysis-2 (SMAA-2), fuzzy flowsort (FFS) and the multi-criteria hierarchy process. Its stochastic nature allows for imprecisions and uncertainty that naturally exist in the particular physical environment of metro stations to be embedded into the evaluation process. The flood risk of 32 stations in Zhengzhou Metro Line 5 during the “7 · 20” rainstorm event is evaluated as a case study. The results accurately indicate that only Shakoulu Station is at high risk, which corresponds to events observed during the rainstorm. Moreover, the risk class characteristics of the remaining stations correspond to historical flooding events. Among them, 10 metro stations are classified as medium risk, 21 are classified as low risk and none are categorized as being at very low risk. Therefore, all metro stations are at risk of flooding although the degree of risk differs between some metro stations. In addition, the validity and robustness of the introduced method are demonstrated by performing comparative analysis and sensitivity analysis. Finally, some managerial suggestions are provided for strengthening the flood control capabilities of metro stations.