Grassy swales reduce and slow down the flow of stormwater runoff and filter out some of the pollutants. Grassy swales have flat bottoms and lots of grass that helps rain runoff spread out and slow down. Sediment (soil) and other pollutants are filtered out as the water soaks into the ground. Grassy swales have taller grass and need to be mowed less often than normal turf areas.
More information on this Green Infrastructure Practice can be found in the Stormwater Management Manual.
Grassy Swale Flow Graphic
Graphic showing how a grassy swale works. Stormwater runoff from rain flows into a grassy swale. Water flows over grass, slowing down the flow and, and allows the pollutants to filter out. Water is slowly released through an outfall structure to a stream.
Maintenance
Checklist for suggested maintenance:
- Is there any trash or debris in the water quality swale?
- Is there any weed or invasive vegetation growth?
- Are there any areas of active erosion?
- Is removal of excessive amounts of sediment at the inflow points?
- Is the appropriate grass height maintained?
- Does the basin have a 95% vegetation coverage?
- Have I submitted my SCM Annual Report?
File Maintenance Report
File your Annual Inspection and Maintenance Report.
Grassy Swales Properly Maintained
Grassy Swales Improperly Maintained