Green streets

Pattern Scale: Neighborhood

Description of the Pattern:

Communities across the world have an increasing need to treat stormwater to eliminate pollutants and to combat frequent flooding due to climate change. Bioswales can be a cost-effective method for stormwater management by planting wetland plants in rocky, loose soil within a contained gardenlike area. Bioswales are commonly added to existing roadways either along a curb, as a median, or even a maintained roadside ditch. Curb cuts allow for water to flow directly or laterally into a bioswale. Stormwater is then directed into a larger sewer system through the assistance of a bioswale or it can catch and hold stormwater from light rain.

Cities like Seattle and Portland have integrated bioswales as part of city streetsscapes, particularly streets affected during large storms, as a tool for stormwater management. Seattle's bioswale project called Street Edge Alternatives Project (SEA Streets) has reduced the total volume of stormwater in a street by 99%. Portland’s Green Streets program uses small-scale vegetated street improvements to manage stormwater runoff at its source. One example is the NE Siskiyou Green Street project, which is estimated to have the capability to reduce the severity of runoff created by a 25-year storm event by 85% by adding bioswales to roads. These examples illustrate the incredible benefits of adding these constructed wetland pockets to roadways by reduce flood damage, which will ultimately save a community the greater expense of flood and disaster recovery.

Bioswales add greenery to what is typically gray space in the built environment. The emphasis of adding native wetland species to a bioswale will not only be beneficial ecologically, but for citizens traversing the cityscape. The wetland species in bioswales and upland species typically found in yards offer the potential for people to take off their "nature blinders" and discover how certain species are able to thrive in one environment and not another.

More about this pattern:

Portland, Oregon, Green Streets Program
Seattle, Washington, Street Edge Alternatives Project

Who Submitted this Pattern:  Rachael Miller