A vegetative filter strip is an innovative water quality control in which runoff is routed as sheet flow through a mildly sloped, well-vegetated area, thus promoting infiltration, sediment deposition, and filtration of pollutants. Because of the need to maintain sheet flow, filter strips are typically used to treat small drainage areas, or areas with low impervious cover. These treatment systems can be used in both Barton Springs Zone (BSZ) and non-BSZ watersheds, but those in BSZ watersheds must be larger. To maintain the proper functioning of these systems the vegetation must not be cut too short (minimum 3” for turfgrass and 18” for bunchgrass), grass clippings must be removed out of the filter strip, and an Integrated Pest Management (IPM) plan is required. Design guidelines for vegetated filter strips are provided in the Environmental Criteria Manual (Section 1.6.7 Alternative Water Quality Controls)
