Impact of Drainage on Green Roof Evapotranspiration
Publication: Journal of Irrigation and Drainage Engineering
Volume 142, Issue 7
Abstract
Green roofs are emerging as an effective technology for stormwater management and sustainable building in the United States as they evapotranspirate the majority of smaller rainfall events (typically 2.5 cm or less) at the source. The various design elements within a roof can enhance or inhibit evapotranspiration (ET), such as the drainage system. Research at Villanova University was conducted on the performance of an undrained (6 years, 2009–2014) and drained (2 years, 2013–2014) green roof. The undrained system evapotranspirated 68–88% of the total precipitation each year between April and November. The drained system evapotranspirated 62 and 56% of the precipitation for 2013 and 2014, respectively. The different drainage configurations dictated the amount of water available for ET; more water was stored yielding more ET in the undrained green roof. The media was able to become fully saturated allowing for the retention of 35 mm of water in the undrained system while the drained system could only reach field capacity (13.5 mm). Accordingly, there was less outflow produced from the undrained system than from the drained system. The lack of drain did not compromise performance during rain events.
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Acknowledgments
The authors would like to thank the Pennsylvania Department of Environmental Protection for funding, Villanova University Facilities Management Office, Villanova Urban Stormwater Partnership (VUSP) partners, and Villanova Center for the Advancement of Sustainability in Engineering (VCASE) for their support.
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Published In
Journal of Irrigation and Drainage Engineering
Volume 142 • Issue 7 • July 2016
Copyright
© 2016 American Society of Civil Engineers.
History
Received: Jul 16, 2015
Accepted: Dec 28, 2015
Published online: Mar 29, 2016
Published in print: Jul 1, 2016
Discussion open until: Aug 29, 2016
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