Flood reduction analysis on watershed of LID design demonstration district using SWMM5

Urban development is the primary cause of the expansion of impervious areas. Urbanization reduces infiltration of rainwater, increases runoff volume, and finally has an effect on the hydrological cycle and urban environment. To solve these problems, Low Impact Development (LID) methods have been used to restore the natural hydrology of predevelopment sites using site design techniques such as infiltration, evaporation, and retention. SWMM5 has been developed as a model to analyze the hydrologic impacts of LID facilities. This study performed hydrologic analysis and evaluated the flood reduction effect of the Jangjae Stream watershed by the design of LID facilities of the rainwater management demonstration district of AsanTangjung New Town (Korea). LID facilities in this study were comprised of infiltration trench, rain barrel, vegetation swale, etc. SWMM5 was calibrated using rainfall data of the 7th and the 14th of July, 2011 and was verified using rainfall data of the 10th and the 11th of August, 2011. This study analyzed flood reduction effect on 50 to 100 y return period. Based on the results of this study, the reduction of flood peak discharge by each return period of storms was estimated to be about 7 to 15%.