Filter strips , also referred to as buffer strips, are small, edge-of-field tracts of vegetated land that are used to reduce the contamination of surface water. They are primarily used in agriculture to control non-point source pollution, however, they may also be used to reduce sediment in storm water runoff from construction sites. In agriculture, they are highly effective in reducing the concentration of nitrogen N and phosphorus P in runoff into surface water   and are also effective in reducing sediment erosion and removing pesticides. The use of filter strips is very common in developed countries  and is required by law in some areas. Filter strips are primarily used in agriculture to control nonpoint source pollution. They function by decreasing the velocity of water, allowing runoff and dissolved inorganic molecules to infiltrate the soil.
Fact Sheet: Grass Filter Strips – MAPC
Filter strips are uniformly graded, gently sloping, vegetated strips of land that provide opportunities for slow conveyance and commonly infiltration. 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. Filter strips are generally planted with grass or other dense vegetation to treat the runoff through vegetative filtering, sedimentation, and where appropriate infiltration. They are often used as a pre-treatment technique before other sustainable drainage techniques e. Filter strips are best suited to treating runoff from relatively small drainage areas such as roads and highways, roof downspouts, small car parks, and pervious surfaces. Filter strips can serve as a buffer between incompatible land uses, and can provide locations for groundwater recharge in areas with pervious soils. Filter strips are often integrated into the surrounding land use, for example public open space or road verges.
Parking Lot Filter Strips
Parking Lot Filter Strips Filter strips are gently sloping, vegetated areas adjacent to impervious surfaces. They are intended to reduce impacts of sheet flow and velocity of stormwater and help improve its water quality. Sometimes referred to as vegetated filter strips, grassed filter strips, grassed filters or buffer strips, they help remove sediments, other pollutants and increase infiltration. Pollutant removal appears to depend on the width of the filter, a feet wide strip being superior to a 75 feet wide strip. Originally developed as an agricultural treatment practice, filter strips have now become a common urban stormwater management practice.
Grass filter strips are low-angle vegetated slopes designed to treat sheet flow runoff from adjacent impervious areas. Filter strips also known as vegetated filter strips and grassed filters function by slowing runoff velocities, filtering out sediment and other pollutants, and providing some infiltration into underlying soils. Because they use sheet flow and not channelized flow, filter strips are often more effective than swales at removing suspended solids and trash from runoff. A filter strip adjacent to this filling station provides room for snow storage and can remove sediment and organics from runoff. Filter strips were originally used as an agricultural treatment practice, but have recently been used in more urban and suburban locations.