Explicit Equation for Estimating Storm-Water Capture Efficiency of Rain Gardens

Rain gardens have increasingly been used to control the adverse effects of urbanization on storm-water quantity and quality. The ratio or percentage of storm water generated from the contributing area of a rain garden that is captured by the surface depression of the rain garden is known as its storm-water capture efficiency. This capture efficiency is an important indicator of a rain garden’s performance for storm-water management. Based on the probability distributions of local rainfall event characteristics and the hydrologic operation of rain gardens, an explicit analytical equation is derived for estimating the long-term average storm-water capture efficiency of a rain garden. The validity of the analytical equation is demonstrated by comparing its outcomes with results from a series of continuous simulations. Example applications of this equation are made for two locations.