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Figure 16: Stormwater Mitigation

Stormwater runoff
Stormwater Mitigation: These graphs show stormwater drainage from conventional (red line) and green (green line) roofs on the University's Butler College dormitories during a light rain event (360mm) in Graph A, medium rain events (600-650mm) in Graphs B and C, and a heavy rain event (1,900mm) in Graph D. In most cases, the green roof delayed, lowered the rate and reduced the volume of stormwater runoff, compared to the conventional roof. As demonstrated by Graph D, which shows three sequential rain events and varied levels of stormwater retention by the green roof, the success of the green roof in stormwater mitigation is directly related to soil moisture content before the rain event. "We continue to collect data for rain and stormwater runoff as well as soil moisture and thermal parameters, and are currently working on mathematical modeling of total stormwater mitigation of the green roof across various storm type events in collaboration with Nitsch Engineering Associates," said Eileen Zerba, senior lecturer in ecology and evolutionary biology, who provided the data for these graphs.