Component: Filter strips
Filter strips are gently sloping, vegetated strips of land that provide opportunities for slow conveyance and infiltration (where appropriate). They are designed to accept runoff as overland sheet flow from upstream development and often lie between a hard-surfaced area and a receiving stream, surface water collection, treatment or disposal system.
They treat runoff by vegetative filtering, and promote settlement of particulate pollutants and infiltration.
Advantages & disadvantages
- Well suited to implementation adjacent to large impervious areas
- Encourages evaporation and can promote infiltration
- Easy to construct and low construction cost
- Effective pre-treatment option
- Easily integrated into landscaping and can be designed to provide aesthetic benefits
- Not suitable for steep sites
- Not suitable for draining hotspot runoff or for locations where risk of groundwater contamination, unless infiltration is prevented
- No significant attenuation or reduction of extreme event flows
Where component can be used
High density: Yes
Contaminated sites: No
Sites above vulnerable groundwater: No
Peak flow reduction: Poor
Volume reduction: Poor
Water quality treatment: Medium
Amenity potential: Medium
Ecology potential: Medium
Filter strips only attenuate the flow slightly but they can be used to reduce the drained impermeable area.
Filter strips are effective at removing polluting solids through filtration and sedimentation. The vegetation traps organic and mineral particles that are then incorporated into the soil, while the vegetation takes up any nutrients.
Filter strips are often integrated into the surrounding land use, for example public open space or road verges. Local wild grass and flower species can be introduced for visual interest and to provide a wildlife habitat.
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