Newsletter and Technical Publications
<International Source Book On Environmentally Sound Technologies
for Wastewater and Stormwater Management>
4.3.1 Filter strips and swales
Filter strips and swales are vegetated surface features that drain water
evenly off impermeable areas (Figure 2.36). Swales are long shallow channels,
while filter strips are gently sloping areas of ground. They allow run-off to
flow in sheets through vegetation, slowing and filtering the flow. Swales also
act to temporarily store and infiltrate the run-off into the ground. Sediments
are removed from the water, and vegetation can take up any nutrients in the
water. Swales and filter strips can be integrated into the surrounding land use,
for example road verges. Local grasses and flower species can be introduced for
visual effect and to provide a wildlife habitat. Maintenance consists of regular
mowing, clearing litter and periodic removal of excess silt.

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