Filter strips

Component: Filter strips

Description

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

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

Residential: Yes

Commercial/industrial: Yes

High density: Yes

Retrofit: Yes

Contaminated sites: No

Sites above vulnerable groundwater: No

Performance

Peak flow reduction: Poor

Volume reduction: Poor

Water quality treatment: Medium

Amenity potential: Medium

Ecology potential: Medium

Quantity

Filter strips only attenuate the flow slightly but they can be used to reduce the drained impermeable area.

Quality

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.

Amenity

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.

Maintenance

Litter/debris removal
Mowing
Repair of eroded or damaged areas