Simulation of Stormwater Flooding Processes in Urban Basin

Stormwater flooding frequently occur in urban basins during rainy period, which is often caused by the even terrain of the cities, the lower design standard of drainage systems, or conduits blocked up by construction waste during urban development period. The methods used to design urban drainage system are not suit to analyze surcharge state of storm drainage systems or simulate flooding processes in the cities. Based on numerical solution of the full St.Venant equations, a mathematical model was established which can simulate gravity flow, pressure flow, circumfluence flow, backwater flow and surcharge flow in the storm drainage systems, and analyze flooding cover area, flooding depth and flooding duration during storm period. The flooding processes simulated in the urban basins can be dynamically demonstrated with the aid of GIS. The model was applied to analyze typical storm events in six drain districts of Shanghai city. The results show pressure flows occur in most sewers and water level of some nodes are higher than ground elevation, and the number of the flooding nodes simulated in the districts accord with what investigated basically, which proves the validity and reliability of the model. The model can be used to provide flood information for flood prevention and disaster reduction for the urban basins.