A mathematical model describing urban rainstorm waterlogging distribution was designed by using 2-D unsteady flow
equations to simulate urban earth' surface and river flows and combining with 1-D unsteady flow equation to simulate
the flow of many secondary rivers and small channels, the dimensions in model of which are smaller than the grid
ones. This model was applied to Nanchang city and different kinds of parameters in the model were simplified based on
the features of the geography and urban drainage pipe systems. The simulated results are similar to real accumulated
water. The errors of the former from the latter are within 20cm (about 83%), but the error greater than 30 cm (about
13%) should not be neglected.