Feasibility analysis of evacuation routes under metro flooding based on 3D modeling of flood inundation dynamics

Metro stations, characterized by enclosed spatial configurations, are highly vulnerable to extreme flooding, posing severe threats to human life and property. Understanding the hydrodynamic processes of flood intrusion and their implications for evacuation routes is therefore essential for urban flood risk reduction. However, the effects of flood intrusion mechanisms and metro drainage capacity on inundation evolution within metro stations remain poorly understood, and evacuation responses following metro flooding have received relatively limited attention. This study employs a three-dimensional numerical model to investigate flood inundation processes under different inflow and drainage conditions. The simulated inundation characteristics are subsequently incorporated as constraints into empirical evacuation formulas to calculate the feasibility of evacuation routes at different locations for different population groups. Taking Shenzhou Road Station of Guangzhou Metro Line 21 as a case study, the effects of station platform door operation, the number and spatial distribution of inflow entrances, and varying inflow depths on flood evolution and internal flow patterns are systematically examined. Based on the simulated hydrodynamic conditions and the derived evacuation pathways, improved evacuation strategies are proposed. Results indicate that the evacuation time for different population groups varies from 516 s to 782 s, with considerable differences, and elderly females require greater assistance. Staircases located farthest from a single inflow entrance or situated between multiple inflow points exhibit the most rapid increase in water depth and should therefore be avoided during evacuation guidance. When metro tunnels facilitate drainage, the station hall floor may temporarily serve as a refuge space, with priority given to transferring pedestrians from the station platform floor to the station hall floor, alongside the implementation of flood barriers at surface entrances. These findings enhance understanding of evacuation planning under metro flooding scenarios and contribute to risk-informed emergency management strategies for flood-prone underground spaces.