(http://www.lakecountyil.gov/Stormwater/LakeCountyWatersheds/BMPs/PublishingImages/bioswale.jpg)
Bioswales are vegetated open channels specifically designed to attenuate and
treat stormwater runoff for a defined water volume. They consist of a swaled drainage course with gently sloped sides
and filled with vegetation, compost and riprap. Depending upon the geometry of
available land, a bioswale may have a meandering or almost straight channel alignment.
A common application is around parking lots, where substantial automotive pollution is collected by the paving and then flushed by rain. Two early examples of scientifically designed bioswales for large scale applications are the bioswale forWillamette River Park
in Portland , Oregon
and one at Carneros Business Park ,
Sonoma County , California
A common application is around parking lots, where substantial automotive pollution is collected by the paving and then flushed by rain. Two early examples of scientifically designed bioswales for large scale applications are the bioswale for
(http://en.wikipedia.org/wiki/Bioswale)
Even where
soils have very poor hydraulic conductivity, a 4 meter swale could reduce the
volume of runoff from a typical local road to about 25% of total rainfall.
Also, as storm water runoff flows through bioswales, pollutants are removed
through filtering by vegetation and soils. In most development situations,
bioswales are well- suited because of their linear nature and because they are
designed to receive storm water runoff via distributed sheet flow.
However,
some researchers point out that when the slope of bioswales become too steep (up
to 10%), runoff velocities become fast enough to cause erosion, and prevent
adequate infiltration or filtering in the channel. Besides, bioswales also do
not seem to be effective at reducing bacteria levels in storm water runoff.
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