GIS-based urban rainfall-runoff modeling using an automatic catchment-discretization approach: a case study in Macau

Rainfall-runoff models play an important role in urban water resource management. The storm water management model (SWMM) developed by the US Environmental Protection Agency (EPA) is a widely used dynamic rainfall-runoff model for analyzing quantity and quality problems associated with urban drainage systems. In an ideal situation, the SWMM model would be designed and analyzed using a collection of catchment modeling systems. Traditionally, catchment discretization for rainfall-runoff modeling is performed manually on watershed maps, a time-consuming job with less-than-accurate results. An alternative approach to catchment discretization based on geographic information system (GIS) is proposed in this paper. The automatic discretization approach was successfully applied to rainfall-runoff modeling in Macau using a SWMM model. The results showed that the proposed approach outperformed the conventional catchment-discretization method in terms of producing meaningful parameters and avoiding most of the tedious preliminary tasks.