RAINSCAPING WITH RAIN GARDENS...
Working With Nature to Transform Stormwater Runoff into Garden Oases

“What is stormwater runoff?
Stormwater runoff occurs when precipitation from rain or snowmelt flows over the ground. Impervious surfaces
like driveways, sidewalks, and streets prevent stormwater runoff from naturally soaking into the ground.”

“Why is stormwater runoff a problem?
Stormwater can pick up debris, chemicals, dirt, and other pollutants and flow into a storm sewer system or
directly to a lake, stream, river, wetland, or coastal water. Anything that enters a storm sewer system is discharged
untreated into the waterbodies we use for swimming, fishing, and providing drinking water.”
Source: www.epa.gov/weatherchannel/stormwater.html

Our manmade system of curbs, gutters, and storm drains quickly carries stormwater runoff directly to local
streams, rivers, and the Chesapeake Bay—without any natural filtering process. However, there are various
techniques we can employ to lessen the detrimental impact of stormwater runoff, such as installing rain gardens,
rain barrels, green roofs, and pervious pavers. This publication focuses on rain gardens.

Imitating Nature with Rain Gardens
Leaving or creating depressions in the landscape promotes stormwater infiltration and reduces stormwater runoff.
Take a walk through a forested area and you’ll notice knolls and swales. Shaping the land in this fashion imitates
nature by creating contours throughout the landscape, which allows rainwater to soak into the ground—as nature
intended. The human tendency is to level the landscape, unaware of the environmental impact of this type of
grading. Rain gardens are simply low-lying, vegetated depressions—generally 3 to 6 inches deep—which have
absorbent soils that temporarily collect stormwater runoff from impervious surfaces and allow the runoff to slowly
percolate into the soil. The depression should be a flat-bottom, saucer shape rather than a bowl shape so that
rainwater runoff can sheet out throughout the garden to allow for better infiltration. This generally takes a few
hours and shouldn’t take more than 2 days. Rain gardens are attractive landscaping features that function like a
natural moist garden, moist meadow, or light forest ecosystem. They can look as informal or as formal as you like.

Rain gardens provide flood control, groundwater recharge, and water-cooling benefits, while the plants, soils,
and associated microorganisms remove many types of pollutants—such as excess nutrients, pesticides, oils,
metals, and other contaminants—from stormwater runoff. Stormwater pouring off hot roofs, pavement, and other
impervious surfaces is temporarily captured, cooled, and allowed to percolate into the ground. Nutrients such
as nitrogen and phosphorus, which would otherwise contribute to algae blooms and other problems in the Bay,
are instead put to beneficial use by being taken up by the plants in the garden. Some studies show that about 50
percent of such pollution comes from individuals and homeowners, through yard care, yard waste, and chemical
pollution from household activities.

Native plant rain gardens also become wildlife oases with colors, fragrances, and the sights and sounds of
songbirds and butterflies regularly visiting. Additionally, rain gardens increase groundwater supplies, significant
because many people get their water from underground aquifers. The replenishment of groundwater—which is
particularly important in times of drought—depends on the absorption of rainwater into the ground.

By creating rain gardens and keeping most of the rain that falls on your site contained on site—the way
nature intended—you can help improve water quality in local streams and rivers and ultimately the Chesapeake
Bay. Native trees, shrubs, and herbaceous perennials improve the ability of water to filter down and recharge
groundwater supplies, unlike turf grass, which tends to form a partially impervious barrier to water infiltration.

Notably, a rain garden is a type of bioretention installation, however, “bioretention” often refers to installations
that are designed and engineered to be more complex than home rain gardens in order to mitigate larger amounts
of runoff. They are deeper and typically incorporate underdrains.

For design and installation instructions, sample rain garden designs, and plant lists, download Rainscaping with Rain Gardens  (2.9mb)