Abstract: Coastal cities are more susceptible to waterlogging disasters in recent years, due to the combined effect of heavy rainstorms and high tides. The division of hazard factors in the areas under such effect is a key factor for deploying disaster mitigation measures. This paper describes a regionalization method of hazard factors and evaluates its application through a case study of the central urban area of Haikou City. We construct a 1D-2D coupled urban waterlogging model based on PCSWMM to calculate the water depth and area of this city’s submerged regions under different combination conditions. The regions are grouped into three types: rainfall-affected, tidal-affected, and joint-influenced; for each type, an optimization analysis of disaster mitigation measures is made. The results show the tidal-, joint- and rainfall-affected regions, in order, gradually become farther away from the coastline. And the reservoirs if arranged in the rainfall-affected region will produce a benefit significantly greater than in the tidal-affected, while the check valves if installed in the tidal-affected region will be more beneficial than in the rainfall-affected. Thus, waterlogging prevention measures are more effective and more efficient through grouping different waterlogging areas.

Key words: waterlogging disaster, coastal city, compound effect, heavy rainstorm and high tide level, risk zoning