Abstract: Urban flood risk zoning maps are of great significance for flood risk early warning and disaster prevention and mitigation. This paper develops a 2-D hydrologic-hydraulic model for linking urban pipe network with surface runoff based on PCSWMM. To formulate a flood risk index system, it integrates the water flow characteristics indexes－including maximum depth, submergence duration, and maximum velocity－with a variety of topographic features: elevation, slope, slope direction, distance from river network, drainage pipe length, and building footprint. Flooding risk zones are delineated using TOPSIS and fuzzy C clustering analysis separately. Comparison of the calculations with observed inundation data shows this hydrologic-hydraulic-statistical analysis model can well predict the spatial distribution of flood risk across the study area. Sensitivity analysis on the choice of water flow indexes and the choice of statistical analysis methods shows that the flood risk zoning generated by the numerical modeling-statistical analysis model is more sensitive to the choice of statistical analysis methods, and less sensitive to the choice of hydrodynamic indexes. Thus, more attention should be paid to the validity of statistical analysis methods for flood risk zoning.

Key words: urban flooding, risk mapping, hydrologic-hydraulic model, statistical analysis, sensitivity analysis