Objectives   Duty of flood prevention is becoming more urgent in recent years because of more frequent waterlogging caused by extreme weather and rapid urbanization. Advanced early warning of waterlogging can help people taking preventive measures to guard against possible trouble. Identification of waterlogging risk is the premise for early warning.

  Methods   The urban hydraulic flood model can simulate the process of waterlogging based on rainstorm forecast and it is a kind of effective method for prevention of loss caused by waterlogging. The method of waterlogging risk identification and warning using detailed hydraulic flooding model of Beijing main city will be introduced. An advanced rainstorm-waterlogging library is formed based on the simulation results of many rainfall scenario for quick identification of a forecast rainfall. The early warning of possible waterlogging in main roads and bridges can be issued after the rainfall forecast through the quick parameters matching of the forecast rainfall and the scenario library. Urban surface is complex and the data quality of drainage facilities is not perfect but they are important factors for model’s simulation results. In this research, multi-mode generalization of spatial data is used to describe the local microtopography as detailed as possible for improving simulation effect. And the surface model and pipe network model are coupled together via various mode according to the quality of drainage data.

  Results   The discharge process calculated by the model is similar to the main peak trend of the measured process. The simulation result of the 1D model was therefore considered to be reasonable. As for the verification of the surface result, the verification effect cannot be measured accurately because the reference data is not ideal. However, the simulation results of all the important bridges were checked one by one according to the familiar departments and personnel, and the simulated waterlogging situation was basically similar to actual situation. The Beijing’s urban flooding model has been put into used during flood season from the year 2018 and served for the flood prevention task of the Beijing main city.

  Conclusions   The urban detailed flooding model can simulate the whole process of rainfall-runoff-convergence and it is suitable for integrated simulation of internal and external flood and waterlogging.