The Penn State Center for Green Roof Research has been conducting studies of extensive green roof systems. One of the first studies is part of a master’s thesis project by Julia DeNardo Hunt. Her research quantified the importance of green roofs in reducing stormwater runoff.
According to Dr. Albert Jarrett, DeNardo’s major advisor and a Penn State professor of Agricultural Engineering, “The benefits of green roofs in attenuating stormwater runoff are largest if one looks at four things: 1) runoff volume reduction, 2) peak runoff rate-reducing, 3) overall runoff delay, and 4) peak runoff delay in these systems.”
Key findings from DeNardo’s study were: 1) green roofs retained on average 6.5 mm (.26 in) or approximately 45 percent of local rainfall during the period of study (two months), 2) peak runoff rates averaged 2.4 mm/hr (.09 in/hr) or 56 percent of the peak rainfall intensity, and 3) runoff from green roofs was delayed an average of 5.7 hours.
Other studies have followed and helped answer other critical research questions. Center Director Dr. Robert Berghage and Dr. David Beattie, associate professor of Horticulture, were interested in media depths and how different green roof plants might respond in these systems with varying drought situations. Last September, the Center received additional funding from American Hydrotech that has enabled the Center to effectively double its data gathering capacity.
BioCycle, Mar 06, p 37, by Drew Mather.