Bioswales and Raingardens


Parkway rain gardens, tree wells, and planter boxes can be designed as vegetated stormwater bioretention features that convey, retain, cool, and cleanse stormwater before being discharged to sewer systems or nearby water bodies. They are installed in parkways, medians, and parking lot islands, and along the sides of buildings to capture roof runoff. These practices are typically designed to allow stormwater to pond slightly and be absorbed and evaporated into the atmosphere by vegetation. Impermeable liners should be used to prevent water from infiltrating into the underlying soils where contaminated soils are present. Excess water is collected by a drain and discharged to storm sewers.



Bioretention practices are appropriate for most new and retrofit projects on individual lots and rights-of-way to accept runoff from roof downspouts, streets, driveways, alleys, sidewalks, and parking lots. In the East Riverfront District, bioretention practices should be used in conjunction with impermeable liners and storm sewers to avoid issues with contaminated soils and leaching.



• Reduces impervious surface runoff volumes (up to 15%) and rates (50% or more).
• Reduces sediments and metals (30 to 70%), nutrients (10 to 30%), and other pollutants from runoff.
• Provides stormwater detention, depending on the thickness of the gravel layer.
• Provides limited habitat for birds, butterflies, and beneficial insects such as dragonflies, which eat mosquitoes.
• Can increase aesthetic value of properties.

PDF Sign In

Please register so that we can follow up with you. Thanks!

* = required