Embrace the Rain: How and Why to Plant a Rain Garden
Stormwater issues are intensifying with climate change. Here's a way to beautify your yard, stave off flooding and possibly snag a tax break.
Stormwater runoff was a problem for Nancy Payne and Ben Goodkind after they bought their Arlington home near Virginia Square in 1998. During heavy rains, the water from their roof (and their neighbor’s) flowed into the same patch of yard, leaving the area chronically swampy.
Replacing their concrete driveway with permeable pavers and installing a porous patio helped—but didn’t completely solve the drainage problem. In 2019, Goodkind decided to try his hand at building a rain garden.
A rain garden consists of a shallow depression or basin (six to 12 inches deep) filled with dense, native plantings that allow stormwater to pool and sink into the ground slowly. Excess water is filtered by the soil rather than running uncontrolled into neighboring properties and storm drains, causing erosion and polluting local streams. By practicing so-called “conservation landscaping,” Goodkind was ahead of the curve on this growing concern.
“With climate change, we are having fiercer, bigger storms and more flooding,” says Barbara Ryan, a sustainable landscape designer and owner of Chain Bridge Native Landscapes in McLean. Consider the events of July 8, 2019, when four inches of water fell on the D.C. area in the span of one hour, flooding streets, businesses and homes. “Conservation landscaping is a critical tool in addressing the effects of climate change,” she says.
Rain gardens have multiple benefits: They’re attractive, sustainable, and create habitats for flora and fauna.
And that’s not all. Arlington homeowners who install them may see less of a hike in their utility payments if the county board approves a new stormwater assessment methodology in 2024. The proposed program would offer credits to those who reduce runoff with rain gardens, rain barrels, native trees, permeable driveways and other forms of conservation landscaping.
Neighboring jurisdictions have similar incentive programs in place. The City of Falls Church offers grant funding through its RainSmart program and reduced utility fees to residents who install these elements. Fairfax County provides funding for conservation landscaping through its Conservation Assistance programs.
For homeowners like Goodkind who are inclined to go the DIY route, Lily Whitesell, a stormwater outreach specialist for Arlington County’s Department of Environmental Services, recommends first conducting a percolation (“perc”) test to measure drainage in the area slated for the rain garden. The test involves digging a 1-foot-deep hole, filling it with water, allowing it to drain for an hour, and then refilling the hole with water and measuring how quickly that water absorbs.
“Typically, what you’re looking for is a minimum of one inch per hour, or even as little as half an inch an hour,” says Whitesell. “You want your rain garden to drain.” Rain gardens are not perpetually wet—a common misconception—but they do need to drain within 48 hours to help prevent mosquito reproduction.
Goodkind admits he skipped this step, solving the puzzle of his yard through trial and error. Eager to get his project underway, he dug a large hole. With the first serious rain, it filled “like a clay swimming pool,” he says—a sign that he needed to amend the soil.
After making the hole even larger (about 10 feet by 8 feet and 1.5 feet deep), he introduced layers of gravel, sand and compost, placing weed-blocking fabric between the layers. He then replaced the dirt and rototilled it, removing roots and rocks. Once the garden bed was primed, ready and draining properly, he and Payne filled it with native plants, such as serviceberry, Joe Pye weed, swamp mallow and native hibiscus. Now, “when we get those really big rains, the rain garden will fill up with water,” he says, “but then [the water will] be gone in a day.”
They no longer have runoff or erosion issues. Plus, the landscaping is pretty and attracts birds and butterflies.
Every property presents its own set of challenges. In 2017, Penrose resident Barbara Fillip installed two 50-gallon rain barrels—which she’d made herself in county-sponsored workshops—in her backyard to capture runoff from her gutters, but they filled up quickly in heavy rains. As a next step, she dug a 6-by-3-foot rain garden, filled the bed with native plants and directed the rain barrels’ overflow into it.
“[I] didn’t want to spend money on it, and it did take several redesigns to make it work perfectly,” Fillip says. She ended up having to dig a little deeper and added a hose that redirects overflow water from one of the rain barrels to her front yard.
She also used rocks to shore up the sides of the rain garden (known as the berm) and to direct any overflow water away from her house.
In retrospect, Fillip wishes she’d done more preliminary research and taken measurements rather than “adjusting as needed.” But she’s happy with the end result.
Some sites do require a higher level of water management expertise. When Mark Johnson moved to Arlington in 2008 to become the operations manager at Fairlington Villages, a community of some 3,400 townhomes, condos and apartments, he had a light-bulb moment while walking his dog near Four Mile Run after a storm. Noting a “muddy sluice of stormwater,” he saw signs warning pet owners to keep their animals out of the water due to pollution concerns.
“I realized that Fairlington, where I worked, is upstream, and there was an opportunity to make a little bit of difference in the Four Mile Run watershed,” says Johnson, a former landscaper and certified master gardener.
He knew that adding rain gardens to the 94 acres of Fairlington Villages could slow stormwater runoff, thereby reducing erosion and pollution in the watershed. Since then, he has installed nine rain gardens. He also plants 50 to 75 native trees each year to sustain the neighborhood’s tree canopy.
Sloped terrain is not optimal for rain gardens, but there are other strategies for tempering runoff in graded areas. Johnson has introduced native plants, as well as strips of rocks and dry wells to prevent erosion and direct the flow of water toward his neighborhood’s rain gardens. (A dry well is an underground cavity lined with stone or gravel that helps manage runoff by facilitating absorption. Filter fabrics and underground perforated pipes may also be used for larger projects.)
Impervious surfaces—roofs, patios and parking decks—are part of our built environment, whether you live on a single-family lot, in a cluster of townhomes or in a multifamily complex. But as Northern Virginia becomes more densely developed with less green space, and as new homes trend larger, occupying a greater percentage of their lots, stormwater needs a place to go.
Back in 2019, Deborah Graze and Steve Montgomery wanted to build a two-car garage behind their 1905 home in Arlington’s Yorktown neighborhood. But they worried that adding a second structure with an impermeable roof would worsen flooding on their property, which was already prone to having a “mud pit with a ton of standing water,” Graze says. They reached out to Adele Kuo, a sustainable landscape designer and owner of Deco Footprint in McLean.
Kuo assessed the site and designed a “treatment train,” recommending that Graze and Montgomery not only install a large rain garden, but also extend the downspouts from their house and garage to flow into that garden, along with an underground dry well system with two storage tanks, which allows that water to percolate into the ground. (Her design also preserved an existing outdoor brick fireplace, sidestepped any negative impact on the property’s tree roots, reduced the size of the lawn, and added a brick patio and walkway.)
The couple planted 11 trees—procured for free through EcoAction Arlington and the county’s annual tree giveaway—including a pin oak, black gums and sweet bay magnolia, which absorb stormwater better than grass and support biodiversity.
If your yard’s topography is complicated, or the upgrades on your wish list are multifaceted, you may want to call in an expert, Kuo says. “If you’re trying to get a firepit in addition to vegetable gardens, in addition to managing stormwater, and you have a slope, you should try to talk to a suitable landscape designer.”
She’s often contacted by homeowners who have a county-required micro-bioretention unit (a “regulated rain garden”) on their property to manage runoff. The retention unit’s placement may be less than ideal and require a little creativity in the landscaping department. Kuo helps clients reimagine how to better use their outdoor space while meeting the required stormwater regulations.
Only after they’d bought their rebuilt Donaldson Run home in 2007 did Maureen Testoni and Mike Flanagan realize they had stormwater and erosion issues on their property. In 2010, with guidance from a county website—and elbow grease from their 11-year-old son, who was excited to build a science project—they installed their first rain garden.
In the years that followed, they removed invasive English ivy, added native plants and reduced the size of their lawn. But they eventually realized they wanted a more systemic approach to water management—plus, they wanted to add a pond for its beauty and wildlife value.
In 2015, the couple hired a landscape designer (now retired) and Evergro Landscaping, based in Glenn Dale, Maryland, to install a series of rain gardens (incorporating the existing one) to better manage stormwater. Now their yard features a tranquil stone pond surrounded by conservation landscaping, including native trees, shrubs and perennials.
Not only is their property free of water issues, Testoni reports, but they’ve seen “a massive increase of animals” enjoying the lush habitat.
Among the frequent visitors are butterflies (including monarchs and zebra swallowtails), dragonflies, bumblebees, skinks, frogs, foxes and a wealth of birds—such as yellow-bellied sapsuckers, bluebirds and the yellow-rumped warbler.
Amy Brecount White practices conservation landscaping in her own yard and is a park steward for an Arlington park.
Why Native Plants?
Native plants are ideal for rain gardens and conservation landscaping because they have evolved to flourish in the local ecosystem, with deeper roots that are better equipped to absorb water. Once established, native plants will thrive without watering, fertilizer or pesticides. They also provide vital food and habitats for bees, butterflies and other insects whose numbers are dwindling, as well as for birds. Plants for rain gardens usually need to tolerate both wet and dry conditions. It generally takes “two to three years for herbaceous plants, and five to 10 years for woody plants to establish and mature,” says landscape designer Adele Kuo of Deco Footprint in McLean.
Native plants are low maintenance, but they do require some light pruning—what Barbara Ryan of Chain Bridge Native Landscapes in McLean refers to as “garden editing.” However, experts like Ryan advise homeowners not to cut back native plants until the early spring, as many creatures overwinter in fallen leaves and branches. Some native bee species nest or lay eggs in hollow plant stalks, so “leaving the leaves” over the winter supports local biodiversity.
For a list of recommended native plants for rain gardens, Montgomery County RainScapes offers rain garden templates and planting plans for various conditions, including sunny and shady spots, multi-levels, a cottage look and deer resistance.
Plant NOVA Natives also provides helpful tips on conservation landscaping and rain gardens.
A New Way to Calculate Stormwater Assessments?
In 2024, the Arlington County Board will vote on a proposal that could change how residential properties are assessed for stormwater fees.
The county’s current sanitary district tax is based on a property’s total assessed value. The proposed stormwater utility system would create a new fee structure based on the amount of impervious surfaces—roofs, driveways and other structures—that don’t allow runoff to soak into the ground. The argument for the change is that “a property’s impervious area is a better measure of how much stormwater each property generates” than its assessed value, according to a county website.
Stormwater assessments pay for a wide variety of programs, including flood resiliency measures, water quality monitoring and pollution prevention, explains Lily Whitesell, a stormwater outreach specialist for Arlington County. If approved, the new stormwater assessment program would follow the lead of the City of Falls Church and Alexandria, which already calculate this utility fee based on impervious surfaces.
While the average Arlington homeowner currently pays about $130 per year in stormwater taxes, the new system would adopt a tiered structure based on a property’s share of impervious ground cover. (The median impervious coverage for a single-family detached property is estimated to be 2,400 square feet.) The new program’s cost for 90% of single-family homeowners is estimated to fall between $230 and $250 per year.
Until recently, Arlington County offered incentive programs through which homeowners could get partial reimbursements for reducing runoff from their property. Similar incentivizing credits are included in the proposed changes.
The county will use its digital mapping system (GIS) to assess a property’s permeability and will have an appeals system. For condos, the impervious area fee will be distributed among the units.