Vegetated Roof Water-Balance Model: Experimental and Model Results

Abstract

AbstractA five parameter, daily vegetated roof water balance model (VR-WBM) was developed, calibrated, and validated by using experimental vegetated roof data from the Seacoast, New Hampshire region. The lysimeter experiment on a sedum canopy characterized water storage with a 0.051 mm resolution. Overall, the results show that the average stormwater runoff reduction was 32% for the study period, and an average reduction per storm was 57%. Average daily evapotranspiration (ET) rates were 1.24 mm/day during the warmest month and 0.52 mm/day during the coolest month. For well-watered conditions, the ET losses were well-modeled by using a grass reference evapotranspiration (ET) value with a crop coefficient of 0.53 for the study’s sedum canopy in which the onset of stomatal closure occurs when the soil moisture is 0.11 m3/m3. When soil moisture content values are lower than 0.11 m3/m3, evapotranspiration rates decrease linearly with declining soil wetness. The VR-WBM does an excellent job predicting runo...