Ensemble Integration of Pedestrian Safety Indicators for Robust Pedestrian Flood Risk Assessment in Urban Inundation Conditions

Increasing rainfall intensity and altered temporal patterns due to climate change pose significant threats to pedestrian safety in highly urbanized areas. Reliable pedestrian safety assessment is therefore essential for evacuation planning and flood risk management. This study evaluated pedestrian stability under various rainfall patterns and return periods using four instability indicators derived from hydraulic and empirical formulations. To mitigate indicator-dependent variability, the normalized indicators were combined into an integrated instability index through an ensemble-averaging approach. The flood-intensity-based indicator systematically underestimated non-walkable areas compared with force-balance-based indicators, whereas the integrated index produced more consistent spatial patterns of pedestrian risk across rainfall scenarios. The most hazardous conditions occurred under the 1 h, Huff fourth-quartile storm, highlighting the influence of late-peaking rainfall on short-duration urban flooding. These findings demonstrate that the proposed ensemble-averaged framework enhances the robustness of pedestrian flood risk evaluation and provides a quantitative basis for prioritizing mitigation measures and evacuation planning in urban areas.