Water Quality Swale (Grassy Swale)

Water Quality Swales can be seen along many of Virginia's roadways, although they are not always designed to treat stormwater. Typically, grassed swales are concave, earthen conveyance systems designed to simply transfer runoff. As a water quality device, a grassed swale is constructed to allow stormwater to soak into the soil, and particles are trapped by the groundcover - usually turf grass. Many swales are constructed with berms (small dams made of earth, rock, or wood) to create temporary ponds that prevent erosion and help promote infiltration of stormwater into the soil.


  • Maintain a healthy stand of grass and mow to a minimum height of 4 inches.

  • Remove trash and sediment

  • Watch for water standing for more than 72 hours, which can indicate clogging of subsurface layers


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