U.S. Water News Online
NEW MARKET, Va. -- Larry Crawford would like to flush terms
like ``gully washer'' and ``mudslide'' from our collective memories,
replacing them with ``bio-retention'' or ``rain garden.''
Crawford, associate director for programs and planning with Prince
George's County (Md.) Department of Environmental Resources,
generally is credited with designing and helping popularize rain
gardens. He also helped nudge them from industrial and commercial
applications to residential landscape use, where they're gaining
``My background is biology and chemistry,'' Crawford says. ``I've
done a lot of work in the wastewater field. We used soil there to
clean wastewater, so I thought I'd like to transfer the idea to the
First, though, he had to lay some groundwork. That included doing
more research, developing new standards and specifications. He also
helped design a manual and then began working toward moving rain
gardens from factory sites to home sites -- all about a decade ago.
``Bio-remediation sounded kind of stiff, so we came up with rain
garden, because that's what they do. They're little gardens that
Stormwater run-off is the nation's No. 1 source of water
pollution, according to the federal Environmental Protection Agency.
Pinpointing polluters is all but impossible because contaminated
runoff is caused by many activities occurring on many different kinds
of landscapes. Agriculture, grazing, mining, forestry, construction,
urban litter, deposits from air pollution and poorly maintained
septic systems collectively contribute to polluted runoff.
``Individual actions such as pouring used motor oil down a storm
drain or applying chemicals to a suburban lawn cause a further
degradation of water quality,'' the EPA says.
That causes algal blooms choking waterways, fish kills, shellfish
restrictions, beach closings and an increasing number of waterborne
One of the best ways to intercept runoff is by building rain
gardens near downspouts, curbs, sidewalks, driveways and parking
lots. Those surfaces often are the fastest routes for impure water to
flow into otherwise clear ponds and streams.
Designers recommend building one or more rain gardens if you
frequently see standing water or erosion in your yard, if you're
concerned about the amount and quality of water flowing from your
property and if you want to attract more wildlife.
``It used to be that landscaping was just a number of planting
projects mounded up,'' Crawford says. ``They were disconnected from
``Landscape architects understand that all we're doing is adding a
cleansing function, making it work for us to control the natural
process that goes on in the soil to clean water.''
Most of the clean-up work is done by the kinds of sediments you
have underlying the gardens, the mulch you layer around the top and
the root systems of the plants you choose.
Biochemical activity helps the toxins that wash down in the
so-called ``first flush'' from a steady rain. The pollutants
transform themselves into harmless compounds like phosphorous and
nitrogen. The roots take up the nutrients.
Start by testing the soil. That will determine whether it has to
be amended to speed the soak rate. Landscapers recommend a blend of
20 percent organic matter, 50 percent sand and 30 percent topsoil.
Some clay -- around 10 percent of the total -- helps absorb heavy
metals, hydrocarbons and other pollutants.
Let water stand too long and your rain garden will serve as just
another mosquito breeding pond. Twenty-four hours to two days is a
good objective, and you can tinker with the infiltration rate while
Size varies but shape often resembles the saucer your grandfather
used for cooling and sipping his coffee. Sink them into low points
around your property -- areas where water naturally flows or
Rain gardens mimic nature. They capture and improve water quality
in much the same way wetlands and forests trap and recharge the peak
flows produced by snowmelt or heavy rains.
Once you're satisfied with drainage, choose your plants. You'll
need varieties effective for filtering runoff from three different
The bottom layer should be aquatic; something that can tolerate
several days of standing water. Middle layer plants should be able to
take a good dunking. Perimeter or upper level plants should be
capable of thriving rain or shine.
Rain gardens can be multifunctional, attractive to birds and
butterflies while at the same time effective for containing and
What kind of plants do you use? Native plants primarily; varieties
similar to those you see in forests, fields and wetlands around you.
They're more disease resistant and require less maintenance than the
``Rain gardens are not only hydrologically functional but they're
enjoyable to look at,'' Coffman says. ``Nature sells. People will pay
more for the added landscaping (in real estate transactions).''
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