Green roofs utilize surfaces on a building to grow vegetation in some type of soil substrate. This practice is not new, but most recently, it has been used to mitigate some of the negative effects of urbanization (e.g., stormwater runoff — quality and quantity). Green roofs have been proven to reduce the total amount of stormwater runoff from roof surfaces while increasing the duration of time that runoff occurs, thus reducing peak flow for rivers in a watershed. Also, green roofs have proven to affect stormwater runoff quality, both positively and negatively. While some studies have shown that green roofs can act as a sink with respect to some pollutants in stormwater runoff, others suggest that green roofs can act as a source for other types of pollutants.In this study, experimental sloped green roof plots were constructed to monitor green roof runoff water quality versus the runoff from conventional shingle and steel roofing surfaces. As a part of the study, two green roof vegetative types (Sedum & native grass) were compared to bare media only and evaluated for storm water runoff quality. From this study, it was determined that the green roofs with vegetation will uptake more nutrients than non-vegetated roofs but few differences could be determined between vegetation types with respect to water quality runoff. Runoff from green roofs proved to be higher for both nutrients and turbidity than roofs with conventional roofing materials; it also was found that green roofs increase pH when compared to roofs with conventional roofing materials.
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