Assessment of Orifice-Controlled Flow Monitoring Device for Rain Garden Performance

Abstract

A high-precision low-flow measurement device that used two different orifices valid over a wide range of small flows measured flow to a rain garden. The design of the device is presented. Direct measurement of the roof runoff with this device was compared with inflow estimates derived from roof area and rainfall data from eight storms. The two methods agree on total inflow volume, although the measurement device captured inflow transients that were not observed in the roof-rainfall estimate. The rainfall-roof estimated inflow data varies in inflow peak time and inflow peak flow rate when compared with the high-resolution monitored inflow data. The inflow measurements were used to assess the infiltration performance of a rain garden in urban Kansas City.