April showers lead to May flowers, but heavy rains can easily over- whelm your city’s sewer system.
In order to manage stormwater volume,
many municipalities require commercial
property owners to implement strategies
that catch or delay the flow of rainwater.
Bioswales, shallow trenches filled with
vegetation, are a permanent way to filter
and clean runoff. Learn how to create and
maintain these passive landscape features.
Natural Stormwater Management
Stormwater runoff is a leading source
of water pollution. As rainwater runs
How Bioswales Provide Aesthetic
REDUCE THE BURDEN OF HEAVY RAINS WITH THIS
EASY-TO-ADD LANDSCAPING SOLUTION
Management and member of the
National Association of Landscape
Under the umbrella of green infrastructure, bioswales are a cost-effective
way to manage inundation from wet
weather events. These conveyance
systems encourage surface drainage
and naturally treat stormwater before it
reaches lakes and rivers. The sloped sides
of a bioswale also slow down the flow of
the water, reducing the burden on a city’s
storm drains during heavy rains.
“Unlike concrete, which delivers all of
the rainwater at once, bioswales send
water in batches,” explains Michelle
Slovensky, Energy Program Manager for
NREL. “By reducing peak storm flow, the
velocity of textured materials during the
conveyance process is lessened.”
The Effectiveness of Green
Bioswales are also filled with dense
vegetation, which uses natural filtra-
tion to remove dirt and pollutants. By
mimicking an ecosystem, bioswales treat
water before it reaches the ground table
or drainage system.
“Plants biologically digest pollutants
by disaggregating chemical compounds.
Bioswales can mitigate everything from
phosphates and nitrates to sulfates and
magnesium,” Slovensky notes.
Specifically designed to handle large
rain events, bioswales allow the water to
percolate at a slower rate than the rain-
fall. Water is absorbed or conveyed with-
in 48 hours, meaning there’s no standing
water that can become a breeding
ground for mosquitos, says Slovensky.
Bioswales can also be linked to a deten-
tion or retention pond so there’s another
opportunity to catch overflow.
Bioswales are often confused with
rain gardens, which function
similarly but are intended
for light to modest rainfall.
A rain garden is a small
depression that is typically
placed adjacent to turf grass
patches or next to a building’s
foundation and sidewalks.
They can include plants and
rocky materials to encourage
“A rain garden is often
created by disconnecting a
building’s downspouts and
directing the rainwater into a
vegetative basin next to the
exterior,” Grover explains.
www.buildings.com BUILDINGS 17
BIOSWALES NATURALLY TREAT WATER as it is filtered through their sloped sides, which also
slow down the flow of water so it doesn’t overburden other stormwater systems.
across impervious surfaces, a number of
contaminants are swept into the stormwater, which is discharged into nearby
waterways. Not only can these pollutants
be toxic to animal and plant life, but the
fast-moving water volume contributes to
streambank and channel erosion.
“As humans develop the world, we
create impervious surfaces. This changes
how water acts when it hits the ground.
Instead of soaking into the soil, the
water carries sediment, chemicals and
auto fluids like oil and antifreeze directly
into the discharge system,” says Bob
Grover, President of Pacific Landscape