DRAINAGE CAPACITY OF RAINWATER PIPE NETWORK IN MOUNTAINOUS URBAN AREAS BASED ON SWMM: A CASE STUDY IN CHONGQING, CHINA

Urban waterlogging brings significant challenges to urban rainwater pipe networks. Chongqing represents a typical mountain forest city consisting of lakes, mountains, and rivers. Due to the topography of Chongqing, it is no uncommon for urban flooding to occur in the region. Therefore, this study used the District of Yuelai Smart as the research region and adopted Chicago Synthetic Rainfall Line to simulate different rainfall scenarios by Storm Water Management Model (SWMM). The study area's surface runoff, node overflow, pipe overloading, and water accumulation in the subcatchment area for four different design rainstorm return periods (T =1, 3, 10, and 50 years) were obtained. The results showed that with an increase of the rainfall return period, the total amount of runoff and infiltration were all increased. Although, the increase of runoff was significantly larger than that of infiltration, the risk of a flood disaster increased. The water volume of five subcatchment areas, which were prone to waterlogging during rainfall, were estimated. It was concluded that the water volume of the subcatchment area had a good exponential relationship with the recurrence period, but had little relationship with the regional area. The causes of inadequate drainage during heavy rainstorms are discussed. This issue was mainly limited by pipelines flowing full for an increase period of time and significant variations, which could provide a technical basis for the construction of urban drainage systems in mountain sponge cities.