#GREEN ROOFS SEATTLE PATCH#

Considering just the land and no drainage infrastructure, the researchers found that implementing green roofs on the entire area of those buildings reduced annual stormwater runoff in the whole watersheds by 10% to 15% with extensive green roofs and 20% to 25% with intensive green roofs. About 10% of the land in these watersheds were buildings (much less than the citywide 26.7% mentioned above). A recent study modeled stormwater runoff in four Seattle watersheds ranging from approximately one to 12 square miles. The City is working towards managing 700 million gallons of stormwater runoff annually by 2025. During heavy or prolonged rain events, the drains connected to sewer pipes can fill up with stormwater runoff and lead to combined-sewer overflows where a stormwater runoff-sewage mixture pours into surrounding water bodies. Now, with so much land replaced by impermeable hardscapes like roads, sidewalks, and buildings, the rain either stays on those surfaces or flows downstream as stormwater runoff, often into storm drains or drains connected to sewer pipes. This vegetation would also sequester approximately 224,062.5 metric tons of CO 2 per year or more.īefore Seattle was a city, much of the rain was absorbed into the soil and used to nourish the abundant forest and vegetation that existed, while some flowed unpolluted into larger water bodies. If 45% of Seattle’s 2015 roof space were covered with vegetation, that would provide more greenspace than all of Seattle’s 489 city parks, which comprise just over 10 square miles.

#GREEN ROOFS SEATTLE PATCH#

These benefits are far more likely to be significant if green roofs are commonplace and widespread across a city rather than a small patch of greenery here and there.

Increased rooftop solar panel efficiency.

With so much potential rooftop space, what are the benefits of more green roofs and elevated green courtyards? Compared to more traditional roofs, there are many possible benefits in addition to carbon sequestration: (Credit: Google Maps) Green roof benefits Semi-intensive green roofs fall somewhere in between.Ī building in Seattle’s Ballard neighborhood contains trees and other vegetation on two levels: an elevated courtyard and the rooftop. Green roofs vary in how ‘intensive’ they are, ranging from extensive green roofs with grass-like vegetation and a thin layer of soil, to intensive green roofs with deeper soil, large bushes, trees up to 30 feet tall, and even amenity spaces. These layers also protect the actual building roof below from plant roots, water, etc. Green roofs also have soil underneath the plants and a set of drainage, filtration, protective, and waterproofing membrane layers which support the vegetation. Most simply, a green roof is vegetation on top of a building. One major solution for increasing vegetation while simultaneously increasing density is wider implementation of green roofs.

(Photo by author)Įvidence shows that concern over tree loss associated with recent development in Seattle has been overblown, but in researching urban greenery, I have become convinced that the city should still institute policies and design recommendations to ensure the amount of trees and other vegetation in Seattle is maintained and even increased as the city develops.

Green roofs can help cities become more sustainable and livable as they grow denser.

Green roofs seattle