Design and Hydrologic Estimation Method of Multi-Purpose Rain Garden: Beijing Case Study

Using rain garden to reduce small catchments area stormwater is very effective for runoff volume reducing, peak rate control and pollution control in ultra urban land use such as Beijing. A design method based on water balance and Darcy's law was put forward in this paper. And then a hydrologic evaluation method was illustrated, including the reductions calculation in runoff volume, peak rate and the total pollutants. A typical rain garden was built in Beijing in recent years, under which, the slag and local sand soil as primary material are installed. It mainly treats the stormwater from small catchments area such as roofs and pavements. Taking Beijing urban area for example, the areas of rain garden were calculated when the return periods and effective depths were various. The method and results provide a foundation for the multi-purpose rain garden design.