Vegetated roofs for stormwater management at multiple spatial scales

Stormwater runoff from impervious surfaces and other urban land cover is particularly detrimental to receiving water bodies in urban centers. A variety of management practices exist to combat the environmental degradation associated with the altered hydrology in urban areas. Vegetated, or green, roofs are emerging as one of these stormwater management tools in the United States. Investigations have primarily been focused on roof-scale processes such as individual roof stormwater retention, plant growth, or growing media composition. Few studies have examined the impact that widespread green roof application could have on the hydrology of a real-world watershed. Using local green roof stormwater retention data, this study modeled hydrologic effects of green roofing scenarios in an urban watershed at a variety of spatial scales. A detailed spatial analysis demonstrated areas of the watershed where green roofs would significantly reduce the total impervious area and provide additional stormwater storage. Hydrologic modeling demonstrated that widespread green roof implementation can significantly reduce peak runoff rates, particularly for small storm events. This analysis recommends the use of vegetative roofs as an abstractive stormwater best management practice in urban watersheds to replicate the interception and evapotranspiration aspects of the water cycle found in less disturbed environments.