Study on the threshold of rainstorm waterlogging in the urban areas of Shanghai

Based on rainstorm waterlogging data from 110 alarm centers and hourly rainfall data from automatic weather stations in Shanghai, the relationships between rainstorm waterlogging and rainfall intensity as well as cumulative rainfall were studied using the method of temporal and spatial process analysis.The rainstorm waterlogging threshold indicators in the urban areas of Shanghai were then established. The results show that the degree of waterlogging in the urban areas of Shanghai is closely associated with hourly rainfall intensity and 2-hour cumulative precipitation.Waterlogging would happen in the urban areas where the rainfall intensity reached 30-40 mm per hour, and waterlogging would increase significantly where rainfall intensity reached 50 mm per hour or 2-hour cumulative precipitation exceeded 70 mm. Compared to the occurrence time of rainstorm, rainstorm waterlogging has an obvious lagging effect with a lag of 1-2 hours in general.Moreover, underlying surface condition, density of population and road also play a role in the occurrence of rainstorm waterlogging.It is a future direction to develop risk scenario simulation and disaster loss assessment of rainstorm waterlogging with comprehensive consideration of the elevation, types of underlying surface, drainage networks and so on.