You are here:
GREENROOF RUNOFF WATER QUALITY
Citation:
OCONNOR, T., R. D. BERGHAGE, D. BEATTIE, AND A. JARRETT. GREENROOF RUNOFF WATER QUALITY. Presented at 2007 CONFERENCE, MINNEAPOLIS, MN, April 29 - May 01, 2007.
Impact/Purpose:
To inform the public
Description:
This project evaluated green roofs as a stormwater management tool. Specifically, runoff quantity and quality from green and flat asphalt roofs was compared. Evapotranspiration from planted green roofs and evaporation unplanted media roofs was also compared, and the influence of media type, depth and drought during plant establishment on plant growth and long term management of media pH were investigated. The goal of the project was to provide high quality replicated data which could be used to develop and refine reliable prediction models of runoff from green roofs, as well as evaluate factors which impact plant growth and establishment. Results indicate that the green roofs are capable of removing 50% of the annual rainfall volume form a roof through retention and evapotranspiration. Rainfall not retained by green roofs is detained, effectively increasing the time of concentration and slowing peak flows for a watershed. There are seasonal considerations as more runoff is generated during winter and for many summer storms there was no runoff. Green roof runoff does contain concentration of some nutrients and other parameters, but values are in line with other planted systems. Due to the volume reduction, actual loadings from green roofs are either manageable at the downspout or loadings are less than flat asphalt roofing.