25 October 2004
growth of trees and shrubs. It is best to avoid working in the riparian area between April
15 and August 15, when a variety of animals are bearing their young.
Corrective Actions. If the buffer width is sufficient, vegetated buffers should
be self-maintaining. Changes in hydrology, drought, over-grazing or natural disasters
such as flooding or fire may require the replanting or reestablishment of the buffer.
GRASSED SWALES are shallow grass-covered hydraulic conveyances that
help to slow runoff and facilitate infiltration.
Figure 8-6. Grassed Swale Schematic
Source: NVPDC, 1991. In EPA, 1999d.
Most Appropriate Uses. The suitability of grassed swales depends on land
use, soil type, slope, imperviousness of the contributing watershed, and dimensions and
slope of the grassed swale system.27 In general, grassed swales can be used to
manage runoff from drainage areas that are less than 4 ha (10 acres) in size, with
slopes no greater than 5 percent. Use of natural low-lying areas is encouraged and
natural drainage courses should be preserved and utilized.28
Schueler et. al., 1992.
Young et al., 1996