Green Roof Storm-Water Runoff Quantity and Quality

Abstract

The design of a green roof plays a significant role in performance. In a ground-level field study, 28 built-in-place green roof models, four modular units, and four roof decks with standard black membrane were arranged in a completely randomized design. Storm-water runoff quantity and quality were monitored from September 2005 through June 2008. Results indicate that green roof systems significantly reduced storm-water runoff and that system design, growth media depth, and presence of plants impacted storm-water retention. In a second study on a building roof, two modular systems were used to evaluate water loss through evapotranspiration. Water loss of both systems was significant and influenced by system design, growth media type, and presence of plants. Finally, runoff quality analyses from the ground-level field study and from a laboratory pot experiment indicate that nitrate, total suspended solids, and turbidity are generally low in runoff after a first-flush event. Runoff water quality was also influenced by system design, growth media type, and presence of plants.