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Green Roofs : A Type Of Green Infrastructure

Decent Essays

Green roofs are a type of green infrastructure that are becoming increasingly more popular as they perform vital environmental functions in addition to being a used for storm water management. In simple terms, green roofs provide storm management by providing layers of absorbent materials on the roof’s surface capable of holding water. These layers consist of some form of vegetation like grass, a growing medium that enables the vegetation to cultivate, a filtering layer that allows only water to pass through, a draining layer, a waterproof barrier that prevents water from going through and the roof structure that is made from a material like concrete, wood or steel (City of Alexandria). According to Lake Superior Streams, green rooftops absorb 15%-90% of runoff rainwater that comes in contact with the roof, and that large variation in absorbency is based on the vegetation and growing medium used (Lake Superior Streams). The type of vegetation used ultimately depends on several factors, such as the climate, access to sunlight and the depth of the growing medium as shallow growing mediums (5cm) can only sustain plant species with short roots such as sedum (stone-crop), while grasses, herbs and wildflowers can be sustained in medium-depth growing mediums (10cm) and columbines and asters can live in growing medium with deeper depths (15cm or more) (Green Garage). The depth of the growing medium directly correlates with the vegetation that can be grown on a green roof as the

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