Photo courtesy Kevin McLean
A raindrop picks up some unsavory souvenirs when it washes over your yard to its destination in the watershed. That puddle of oil under your car, the pesticides on the patio, some fertilizer from the lawn, and the bacteria in the backyard where the dog is prone to go — they all collect in a toxic cocktail of chemicals.
Today’s residential landscape is a patchwork of what professionals call green infrastructure and gray infrastructure. Green infrastructure is nature’s idea of what the world should look like. Man added gray infrastructure (roads, parking lots, roofs and walkways) to make the world more livable. Gray infrastructure collects rainwater in runoff, directing it into storm drains and waterways and carrying pollutants with it, instead of allowing the rain to soak naturally into the ground.
Something as simple as a shallow depression in your yard filled with native plants can help trap and treat contaminated storm water. It’s called a rain garden.
Water moves in a continuous rhythm of evaporation, condensation, precipitation and collection called the hydrologic cycle. Nature manages excess nutrients, pathogens and sediment as part of the process. When you insert a rain garden into the hydrologic cycle to capture runoff before it reaches the storm-drain system, it mimics nature by slowing infiltration, allowing plants to filter pollutants and soil to trap suspended solids. The system can help prevent local flooding, protect the watershed, recharge local groundwater and even control mosquitoes. City of Richmond residents whose rain gardens reduce the amount of runoff from their properties into storm drains can file a storm water credit application with the Department of Public Utilities. The Virginia Conservation Assistance Program provides cost-sharing incentives to residents in surrounding counties.
Kelly Fleming is a senior landscape architect at the Low Impact Development Center, a national research organization dedicated to promoting sustainable storm water management solutions.
“Slow it down. Spread it out. Soak it up,” Fleming says, explaining the principles at work in a rain garden. Plants intercept water that collects on their leaves, where it evaporates. Root systems absorb water. Soil filters the balance before it can foul the water table.
Choose a spot for your rain garden where the soil drains well. (You’ll need to do a perc test. The goal is to filter rain, not collect it. Make sure it drains within 24 to 36 hours.) Site it downslope from a driveway, roof, patio or walkway, and position downspouts to direct storm water toward it.
“A rain garden’s size is determined by the amount of water you intend to treat,” Fleming says. A space that is 20 to 30 percent the size of the impervious area you’re compensating for is ideal. The shape of the rain garden can vary to fit the space available.
Populate a rain garden with deep-rooted native plants. “Because they are adapted to local soil and climate conditions, natives are relatively drought tolerant and pest/disease resistant,” Fleming explains. “They also provide food and habitat for local wildlife and beneficial insects.” She advises homeowners to plant species that tolerate high levels of moisture at the base of the depression, and those that tolerate both dry and wet conditions as you move toward the depression’s outer edges, where plants should be more drought-tolerant.
Done correctly, a rain garden is an attractive DIY project that can have a big environmental impact. It’s an elegant solution to a dirty little problem — a way to restore water to its original purity and make it, well, right as rain again.
