Pervious strips are long, linear landscaped areas or linear areas of pervious pavement that capture and slow runoff. Depending on the underlying subsurface soil conditions, pervious strips can provide some infiltration, but to a much lesser extent than bioswales. Pervious strips offer an inexpensive initial step in urban stormwater management but are unlikely to provide enough capacity for treatment of a street’s full water quality event.
Critical
1Integrate pervious strips with sidewalks, medians, curbs, and other features. Depending on the desired configuration, pervious strips may treat either sheet flow or more channelized flow. Pervious strips require long, continuous spaces to treat and filter pollutants.
2As required, install a perforated pipe at the base of the facility to collect the treated runoff.
Use a maximum 2% gentle side slope to direct flow into the facility.
Protect adjacent subsurface infrastructure by maintaining a minimum clearance, installing waterproof liners as separation barriers, or by constructing a deep curb to separate the roadbed subgrade or parallel utility line from the facility.
Recommended
Where possible, cluster public furniture and utility appurtenances to maximize the contiguous linear space for pervious strips and minimize conflicts.
Design the volume and flow capacity based on the contributing watershed area and design storm runoff.
Infiltrate if underlying soil is of an appropriate type for infiltration and there are no conflicts with underlying utilities.
3Reduce irrigation requirements of pervious strips by utilizing pervious pavements and native plants. Native landscaped areas are generally preferable because they will generate less runoff and can help mitigate the urban heat island effect. Native plants increase biodiversity, act as a pollinator habitat, and are well-adapted to the regional climate, increasing their chances for survival.
Use a “green gutter” design with a flat bottom and vertical containment system.1 This includes a very shallow (maximum 4-inch stormwater runoff detention) and thin (maximum 3-feet cross dimension) linear facility.
Optional
For additional runoff control on slopes exceeding 4%, consider the use of adjustable weirs, berms, check dams, or modified catchbasins that feed into the bioswale or permeable system.
Long, linear spaces may be integrated with urban agriculture programs.
- Nevue Ngan Associates et al. Stormwater Management Handbook, (Washington, D.C.: U.S. Environmental Protection Agency, 2009), Chapters 5–6. ↩︎
Urban Street Stormwater Guide
Learn more about stormwater in NACTO’s Urban Street Stormwater Guide