| Tools for predicting rain garden performance are limited, particularly for predicting seasonal performance. Changes in temperature cause changes in the viscosity of water, infiltration rates, and evapotranspiration rates. A variably-saturated soil model, HYDRUS-1D, was calibrated and validated using observed ponding depth and soil moisture data for the Philadelphia Zoo Rain Garden, owned and operated by the Philadelphia Water Department (PWD). Warm and cold seasons were simulated with typical meteorological data and temperature-adjusted saturated hydraulic conductivity values. Design-storm simulations confirmed that the rain garden is over-performing. Maximum capacity of the system was simulated by increasing the loading ratio until overtopping occurred or ponding remained longer than 24 hours. This study will demonstrate how modeling of an operational urban rain garden offers a realistic picture of performance and could be used as a tool for informing regulations and design. |
