Operation of Cap Orifice in a Rain Garden

Abstract

AbstractThe rain garden is one of the most commonly used, low-impact development (LID) devices. Rain gardens are designed to reduce runoff volume, delay peak flow, and improve water quality in stormwater. A rain garden consists of surface and subsurface components: The surface component is a storage basin that stores the water quality capture volume (WQCV), whereas the subsurface structure is formed with a two-layered filtering medium. The drain time is the most important design parameter for the rain garden’s operation. A short drain time will lead to an inadequate residence time for the sedimentation process, whereas a long drain time will result in potential hazards to the public. A new rain garden usually has a high infiltration capacity through its filtering layers. Over years of service, the clogging effect will slow down its infiltration rate. To improve the performance of a rain garden through its life cycle, it is recommended that a cap orifice be installed at the outlet of the perforated underdr...