Managing Stormwater Runoff With Rain Barrels and Rain Gardens
Question: Whenever it rains, water pools in low spots in my yard. How can I fix the problem myself inexpensively and not have runoff possibly pollute local streams?
Water that pools in yards can be a problem for many reasons. It kills grass, can damage some plants, and can be a breeding ground for mosquitoes. In developed areas, stormwater runoff carries pollutants including fertilizer, pesticides, auto fluids, animal waste and trash over impermeable surfaces into the groundwater, rivers, streams and eventually the Chesapeake Bay. Runoff also erodes and degrades soil, aquatic habitat.
Rain barrels and rain gardens can be good solutions for homeowners who want to do the work themselves and are on a tight budget.
A rain barrel captures rain from the roof via the gutter system. It typically holds 40 to 60 gallons. The water is then saved for watering gardens and lawns, filling birdbaths and outdoor water features and for other non-potable uses. Since the water collected is not treated, it should not be used for cooking, drinking or bathing. In addition to providing a free source of water for homeowners and reducing the harmful effects of runoff, rain barrels and other rainwater harvesting techniques can reduce peak water demands, demands for treated drinking water and the burden on water treatment facilities.
Building Rain Barrels
Commercial rain barrels can be expensive—the average cost is between $120 to $160 depending on the size, but the cost can be reduced substantially by making them yourself, using cast-off food grade barrels and hardware store parts. Building a rain barrel involves connecting the barrel to a downspout, installing a spigot near the bottom of the barrel to draw water and providing a pipe or hose to handle the overflow when the barrel is full. Concrete or wood blocks are used to provide a stable, level base for the barrel.
With only ¼ inch of rainfall, runoff from an average size roof will fill a 55-gallon barrel. Because barrels fill quickly, the overflow should be directed away from the house and into areas that can handle the excess water. This is accomplished by directing the overflow into additional rain barrels or to other parts of the yard where it will seep into the ground.
Rain barrels are fairly easy to maintain in good working order. Check the gutters, downspouts, barrel spigot and outflow to make sure they are not clogged and inspect the rain barrel for leaks periodically. In cold climates, the barrels should be drained and spigots left open to prevent winter damage from freezing temperatures.
The Chesapeake Bay Program cautions that making a rain barrel is not a quick or easy job for those with limited experience in similar “do it yourself” projects. However, for those with some expertise, there are many online guides and YouTube videos that will lead one through the process. In addition, Cooperative Extension offices, Soil and Water Conservation Districts and other environmental groups offer workshops that provide “how to” guidance on building rain barrels. Both the City of Charlottesville and Albemarle County Service Authority offer a $30 rebate on newly-purchased rain barrels, with a limit of two per household.
A rain garden is a natural or man-made planted shallow depression that temporarily holds stormwater runoff from impervious areas for a few days, allowing it to evaporate, be absorbed by plants or infiltrate (seep into) the ground. Also known as a bioretention basin, a rain garden can slow down large volumes of runoff so that the plants, soil and microorganisms in the garden can filter and remove pollutants naturally. The filtered stormwater can also help recharge the local groundwater supply. It is an eco-friendly way to manage areas of standing water that drain in two to four days. Sometimes called a “puddle with plants”, rain gardens also add beauty to your home landscape and enhance wildlife habitat.
Constructing Rain Gardens
Rain gardens can be located in a sunny or shady area where runoff occurs naturally or where runoff can be directed by pipes or swales. Be sure to have your local utility locator mark any buried utility lines first so that the rain garden is located away from them. Do a soil test to determine the pH and determine and if any lime, fertilizer or other amendments are needed. Applying amendments only when needed minimizes nutrient runoff into surface and groundwater. Rain gardens do better when clay content is not high, although some clay content is desirable because it will absorb certain pollutants. In addition, a perc test, which assesses how readily the soil absorbs water, should be conducted to be sure the garden will drain properly.
Locate the rain garden at least 10 feet away from buildings. Before digging or amending the soil, determine the appropriate dimensions needed to accommodate stormwater runoff. The Virginia Cooperative Extension offers a guide to help with this calculation, based on the surface area of the impermeable surfaces (i.e., roofs, pavement) supplying the water.
Rain gardens can overflow during very heavy rainfall, so managing the excess water should be accounted for in the design. Very large drainage areas, such as in subdivisions, have special installation requirements but can still use stormwater bioretention practices to filter stormwater.
The bottom of rain gardens should be at least 2 feet above the high-water table and the depth should be 6 to 8 inches lower than the surrounding area. They are usually dug and graded deeper because organic material, plant root balls and mulch will raise the level of the rain garden’s bottom over time. The garden should drain within 2 to 4 days; the goal is to avoid creating a bog or mosquito breeding ground.
Rain gardens are a great place for native plants. Select plants that are able to tolerate both wet and dry periods. A layered approach that includes native shrubs and grasses, perennials, and ground covers (and trees, if the area is big enough) works well to control runoff and provide food, shelter and nesting spots for wildlife. In addition, a grass buffer strip can also be used to slow the water as it enters the garden. Use a good soil mixture and top everything off with a layer of mulch.
Other Options for Control of Stormwater Runoff
Depending on the site, different types or a combination of stormwater management strategies may be more appropriate. Virginia Cooperative Extension has a series of helpful fact sheets that cover rooftop redirection, permeable paving, grass swales and buffers. Planting trees will also help. Research has shown that mature trees take up an average of 20 percent of annual rainfall in their canopy and increase infiltration.
Rain barrels and rain gardens can be good ecological solutions to control stormwater runoff. They can be installed by homeowners successfully and economically when guided by the resources listed below or, when the job is too big or complicated, with the help of stormwater management professionals.
“Attractive Ways to Manage Stormwater Runoff” Piedmont Master Gardeners., 8 Mar 2023.
“Carolina Clear Presents: How to Make a Rain Barrel”, A Public Service Announcement of Clemson, University, YouTube video.
“Putting the Brakes on Stormwater Runoff”, Piedmont Master Gardeners, 10 Mar 2021.
“Rain Gardens” Fox, L. J., Research Associate, Horticulture, et. al., Virginia Tech, Virginia Cooperative Extension,Stormwater Management for Homeowners Fact Sheet 5. Virginia Cooperative Extension, Publication SPES-13, 2018.
“Rain Gardens: A Landscape Tool to Improve Water Quality”, Virginia Department of Forestry,2012.
“Rain Garden Plants”, Andruczyk, Mike, Extension Agent, Chesapeake and Fox, Laurie, Horticultural Specialist, Hampton Roads, Agricultural Research and Extension Center, Virginia Tech, Virginia Cooperative Extension, Publication 426-043, 21 Dec 2018.
“Soak Up the Rain: Rain Gardens”, U.S. Environmental Protection Agency, 24 Mar 2023.
“Stormwater Best Management Practice: Bioretention (Rain Gardens)”, U.S. Environmental Protection Agency, EPA-832-F-21-031L, Dec 2021.
“Water Quality and Conservation”, Chapter 17, Virginia Cooperative Extension Gardener Handbook. Blacksburg: Virginia Cooperative Extension. Licensed with CC BY-NC-SA 4.0. 2023.