Green Street designs promote infiltration of groundwater through various strategies. Pervious pavement and bio-retention swales are two strategies. Ideally water would enter swales by sheet flow, as on Merlo Court in the second example below. Curb cuts, like those on 155th Avenue in Beaverton, are a common way to direct water to swales. Though curb cuts concentrate the flow, curbs may be desired for safety considerations or may be less costly than removal of curbs for retrofit projects.
155th Avenue
Beaverton Green Street
In 2006, the city of Beaverton has installed some “green street” features on 155th between Bristol and Middleton Court. A close look at the sidewalk on the west side of the street may remind you of Rice Krispie treats. The concrete is porous allowing water to pass through. Between the sidewalk and the street is a bioswales, a ditch filled with native plants to filter out sediments and allow water to infiltrate. Cuts in the curb allow water to run from the street into the swale. The east side of the street is planted with fir and cedar trees to catch falling rain.
CWS Field Operations Center
2025 SW Merlo Court, Beaverton
Merlo Court, the street in front of the facility is curbless, allow “sheet-flow” of water into the beautifully landscaped bioswales. Parking lots are paved with both Uni Eco-stone pervious pavers and porous concrete. Bioswales with native plants separate the rows of parked cars. Monitoring of stormwater data from this site will help direct future development of LID technology. CWS has published Slow the Flow, a booklet describing the costs, installation, advantages and limitations of each of the LID features on this site.
