Evaluation on implementing green stormwater infrastructure to reduce runoff and conserve water in Banyumanik, Semarang

Abstract Flood problems do not always occur identically in areas with low-lying topography or coastal areas. Floods also often occur in areas with relatively high topography, for example in the Jalan Dr. Setiabudi Banyumanik Semarang. In some places the area is concave, the drainage system is inadequate so flooding often occurs. The aim of this study is to evaluate the existing drainage capacity and to analyse efforts to plan a sustainable urban drainage system by implementing Green Stormwater Infrastructure (GSI). The GSI type is adjusted to land availability and soil characteristics. Hydrology and hydraulics analysis methods are used is SWMM 5.2. Based on a combination of spatial, hydrological and hydraulic analysis of existing conditions, 55 overflows were obtained. Efforts to reduce runoff are planned by placing GSI in locations where the land is available. The area that allows GSI to be implemented is around 28.4 Ha of 67.9 Ha total drainage catchment area, with GSI in the form of 343 infiltration wells, 1.0 m in diameter with a depth of 5.0 m. Implementing infiltration wells can reduce the total runoff upto 23.32%. To deal with excess runoff, the channel dimensions have been enlarged, especially at the outlet in the downstream area.