This is the final article in a three-part series exploring stormwater management strategies implemented by Extension Master Gardeners in Alexandria and Arlington, Virginia. In addition to being environmentally sound, these local government-approved practices can lead to utility fee reductions.
If you missed them, read Part 1 and Part 2.
By Elaine Mills, Extension Master Gardener
Beverly, a resident of North Arlington who has been mitigating stormwater problems for 25 years, offers this advice to others:
- Residents should be observant and ready to make changes over time to address water problems.
- Construction in the region is creating more impervious surfaces, which, combined with the greater number of intense storms resulting from climate change, leads to greater problems with runoff and flooding.
- An increasing number of residents are having to deal with water rushing through their properties from other people’s yards, making it important to work with neighbors.
- Loss of trees, such as big oaks, and the presence of underground streams pose additional concerns in finding stormwater solutions.
Rain and Bog Gardens & French Drains and Dry Creek Bed
Beverly has found that a combination of engineering solutions along with good plant choices has helped her deal with excess water.
- Fifteen years ago, she constructed a rain garden along one side of her sloping backyard to deal with excess stormwater from rain events. This depressed area in the landscape is filled with moisture-loving plants, including dwarf bald cypress, hydrangea, Virginia sweetspire, fothergilla, ostrich ferns, pitcher plants, and mayapple. The garden needs to be maintained and re-dug periodically.
- Due to increased water volume accumulating near her house, she directed downspouts to a French drain beneath a sloping garden path in the middle of the backyard. This trench is filled with a flexible perforated pipe that is surrounded by lightweight expanded polystyrene nuggets that are held in place by a mesh sheath. This system filters soil from the flow before sending the water underground.
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When she later observed that overflow from the pond behind her house caused the path to wash out, she added arborist’s wood chips and constructed a second French drain that runs beside the path from the middle of the yard to a bog garden at the base of the slope. This area where the soil is permanently moist but not waterlogged is planted with native species that include hibiscus, ironweed, cardinal flower, turtlehead, American beauty-berry, sweet-shrub, and sensitive fern.
- Another serious problem Beverly faced was stormwater flowing from an uphill neighbor’s property across her backyard and into the yard of her neighbor on the other side. To prevent water washing out areas of the yard, Beverly cooperated with her neighbors and designed a dry creek bed which connects to the yards on both sides. Water flowing through during rain events is now slowed and filtered before being directed to a storm sewer that empties into a tributary of Lubber Run.
Kathy, another resident of North Arlington, needed to construct a rain garden in her front yard to deal with huge amounts of water flowing from construction of three large homes uphill.
- A landscaper removed her sod, excavated three feet down, added a truck-load of mulch, and created a berm to keep water off the adjacent public sidewalk.
- During storms, water fills up to the level of the sidewalk and is then absorbed.
- Native species in and bordering the rain garden include ostrich fern, ground cherry, cardinal flower, swamp sunflower, and red osier dogwood.
- She advises to be sure to select native iris species, such as Virginia Blue Flag (Iris virginica) rather than the invasive Yellow Flag (Iris pseudacorus) and to be aware of the vigorous spread of plants like orange coneflower.
Mary Nell, a third North Arlington resident, is very pleased with her long, decorative driveway designed by a local landscape architect. The permeable pavers do an excellent job of preventing stormwater runoff.
Alyssa’s garden in South Arlington is an excellent example of the use of a dry well. She wanted to capture a large part of the water from her home’s roof to retain it on her property, preventing runoff, and using it to water the plants to be added in a new landscape design in her front yard.
- Her original plan was to collect water from two downspouts on the side of the house and to have it flow directly through a pipe into the garden. Unfortunately, due to regrading of the soil, the pipe could not be easily brought to the surface in a pop-up for use of the water near the house.
- A percolation test conducted by her crew indicated that the pipe could not safely be allowed to discharge water in the middle of the yard. The heavy layer of clay soil didn’t allow the water that was poured into the test hole to be absorbed quickly enough.
- An alternative solution was the construction of a dry well below the clay layer of soil. The crew used a bobcat to dig a deep hole which they lined with several inches of gravel before inserting a perforated plastic barrel to receive drainage water and allow it to percolate away.
- In rainstorms, the dry well starts draining immediately, and rainwater flows into the ground, watering the roots of Alyssa’s fringetree and eastern redbud. The device rarely overflows, but an overflow pipe bordered by rocks and plantings of deep-rooted Little Bluestem grass can handle any excess water.
- Four rain barrels connected in pairs collect water from the home’s two additional downspouts.
Extension Master Gardener Cheryl has some final words of advice for area homeowners dealing with stormwater issues:
- The Stormwater Utility Fee in Arlington County is not a new assessment. The method of calculation is changing to better correlate with the amount of stormwater each property generates.
- It can be helpful for homeowners to observe the flow of water in their gardens by standing outside with an umbrella during a storm.
- Water will back up and flow into yards when debris is placed or collects at the curb.
- Lawn is not very permeable, and water can remain puddling for several days. Replacement of turf grass with native plants leads to absorption within several hours.
For more information about how to create a rain garden and what plants are appropriate, see Rain Garden Plants, Virginia Cooperative Extension Publication 426-043 as well as multiple presentations from the 2021 Rain Garden Workshop organized by the Northern Virginia Regional Commission. Information is also available on backyard bogs from UNC Charlotte Urban Institute.