One of the major problems urban and suburban areas encounter is managing storm water run-off due to the amount of impervious surface (i.e. streets, sidewalks, buildings). During a storm, rainwater sheds off of these surfaces into the sewer, nearby lakes, streams, or other bodies of water carrying along with it pollutants such as fertilizers and oils. Much of the pollution in our water bodies comes from storm water run-off. You may think that your home, driveway, and sidewalks don’t have much effect on storm water run-off, but combined with all your neighbors it starts to add up. Installing even a small rain garden in your yard has great benefits.
What is a rain garden?
A rain garden is a depressed, tear drop shaped area designed to collect and absorb storm water. Storm water is directed from your downspouts or flows across the lawn into the rain garden where it slowly filters through the soil, thus helping to mitigate large amounts of water and pollutants from going directly into the sewer system. Rain gardens are an affordable, aesthetically pleasing, an efficient way to manage storm water on your site. Paired with other methods of Low Impact Development (LID), such as permeable paving, green roofs, and rainwater harvesting systems, for addressing storm water run-off, you may be able to reduce or eliminate most of the stormwater run-off from your site.
Location and Design
Rain gardens are relatively easy to install yourself in your own yard, though some careful planning is required to determine the location, size, and materials to be installed. Ask you architect, landscape architect, or landscaper if you need assistance with designing your rain garden. Here are a couple of tips for locating your rain garden: 1) Locate a minimum of 10′ from your house to prevent water from flooding your basement, 2) Locate in area with full sun, 3) Do not install over a septic system, lines or pipes, and 4) Do not install in an area that currently does not drain well. When you have selected the location for your rain garden, one of the first steps is to check the condition of the soil to see how well it drains. A soil test should be performed. Next, it is recommended that 12″-24″ of amended soil be added in your garden to maximize percolation. The garden should be sizes appropriately based on the amount of impervious surface that you are directing the water from. The rain garden contains three planting zones: 1) topmost zone is least wet, 2) middle zone has occasional standing water, and 3) the bottom (lowest) zone will be the wettest condition. A variety of plants can be selected and installed that tolerate the varying zones. Be sure to include a variety of flowers, grasses, and shrubs with varying sizes, heights and blooming times. Choosing native plants is typically a great approach and tends to help attract good insects and birds. Your rain garden will require standard maintenance like a regular garden – regular weeding and watering during the first 2-3 years.
For more information on designing or installing a rain garden, refer to the WSU Rain Garden Handbook.