The Stormwater Control Potential of Green Roofs in Seattle

Green roofs are engineered landscapes designed for the roofs of buildings. The stormwater management benefits of green roofs have frequently been cited as a compelling reason to promulgate the greening of urban rooftops. The most commonly reported stormwater benefits of green roofs are reduction in flow volumes and reduction in peak runoff rates due to flow attenuation. International research has demonstrated the benefits offered by green roofs; however, efforts to quantify and monitor benefits achieved in specific climatic regions of the United States have only begun in recent years. This paper presents field performance data and computer simulations for green roofs in the Pacific Northwest maritime climate. These show that green roof performance varies greatly but all of the evaluated systems reduced peak runoff.