The feasibility of reducing storm water runoff using green roofs

Abstract

Green roofs are where a roof of a building is partially covered with vegetation which acts as a means of providing flow control by attenuation, storage and losses due to evapotranspiration. A green roof consists of several-layered materials to achieve the desired vegetative cover and drainage characteristics. Through using InfoWorks Integrated Catchment Modelling (ICM) and the software’s integrated Sustainable Urban Drainage (SUD) control editor, simulations were run using Time Series Rainfall (TSR) rainfall over a long continuous period of 10 years. The effects green roofs have on reducing the runoff from roofs and the attenuation of the flow to the sewer system within Plymouth city centre could then be analysed. The most reliable outcomes from the year of 2004 was analysed to present comprehensive results. The main findings of this study provided evidence that green roofs are very beneficial and have the potential to reduce the runoff by up to 15% via evapotranspiration and attenuating flows reaching the sewer system. The type of green roof installed has also been shown to have a significant impact on the retention rate with intensive green roofs being 1.9 times more effective than extensive roofs.