About Green Streets?

Green Streets are neighborhood streets with stormwater management features, often utilizing natural elements, which can remove and filter storm water runoff before it reaches the storm drain. These features are visible from the street, allowing interaction by the public by opportunities for maintenance and upkeep, and education about human interaction with the natural environment.

You may want to check out the Portland Bureau of Environmental Services “What is a Green Street?” flyer for a succinct overview.

swale diagram

Bioswales, also called biofiltration swales or grassy swales, are one possible feature of Green Streets.

“Swales are gently sloping depressions planted with dense vegetation or grass that treat stormwater runoff from rooftops, streets, and parking lots. As the runoff flows along the length of the swale, the vegetation slows and filters it and allows it to infiltrate into the ground. Where soils do not drain well, swale are typically lined and convey runoff to a drywell or soakage trench. Swales can include check dams to help slow and detain the flow. A swale can look like a typical landscaped area.”

-The Portland Community Watershed Stewardship Program Stormwater Solution Handbook

Bioswales often integrate into green streets at curb extensions where upstream and downstream cuts in the street curb allow rainwater to exit the street and filter through the swale. Overflow exits through the downstream curb-cut and continues to the storm drain.

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3 responses to “About Green Streets?

  1. Wow-I learned a lot. I had never heard of a bioswale, but can imagine they could be of great importance in a Pacific Northwest location such as Portland. Not only do they work hard but they look great too. Congratulations–I look forward to learning more and seeing the progress of the bioswales already constructed! Perhaps the project could be hilighted at OMSI-if I recall they have a whole section dedicated to the watershed.

  2. Bridger Wineman

    Bioswales are a reletively new idea for most of us. The concept really turns traditional assuptions about water treatment and city infrastructure its head.

    I haven’t seem the OMSI exhibit you mention. We’ll have to check that out.

    Thanks for the encouragement.

  3. Erika Johnson

    OMSI actually developed one of the region’s first parking lot bioswales to treat storm water on site when its facility was developed.

    As of 2008, the OMSI bioswales have been infiltrating stormwater runoff for nearly 17 years and they are a model for other stormwater management projects.

    The parking lot bioswales at OMSI demonstrate Portland’s first large-scale, on-site stormwater treatment and infiltration facilities. Before installation of the swales, over 522,000 cubic feet of untreated stormwater runoff discharged directly to the Willamette River annually.

    Learn more at: http://www.portlandonline.com/shared/cfm/image.cfm?id=78489

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