A Landscape Feature that Helps Protect Water Quality

Source(s): Steve Brady, Cobb County Extension

How can your landscape help protect water quality? By installing a rain garden you can have an attractive display of interesting colors, textures and forms that improves water quality.


A rain garden is not a bog garden or a swamp. It is designed to receive some of the water that pours off of your driveway, roof or other impervious surfaces. Instead of sending it rushing off to the nearest storm drain or stream, the water is allowed to slow down and pause long enough for some of it to soak into the water table. This helps reduce the volume of water that scours our creeks. In addition, the water that exceeds the pool capacity of your rain garden has a moment to settle out soil particles, fertilizers, chemicals, etc in a process called biofiltration.

Naturally people think a rain garden will breed mosquitoes. If properly constructed, the water that is held in the garden will perk into the soil in 24 to 48 hours after a rain event. Mosquitoes need more than three days to breed in calm water.

Construction of the garden is not without challenges. The Demonstration Rain Garden here in Cobb County met and overcame several. A stormwater channel carries water off of the highway and runs next to our rain garden site. Just days before we started construction, a 4 inch rain event filled the channel and water backed up to the Cobb County Water System’s back door. Before we could go any farther the channel had to be re-engineered.

The next challenge stemmed from the fact that this location was once used as a steam locomotive factory. Te soil was not only extremely compacted, but also had a pH of 7.8 (very high) due to all the ash. After much plowing, grading, amending, and tilling the rain garden was functional.

Today the garden not only reduces runoff and pollution, it also serves as an environmental education site, and place for plant evaluations. It adds beauty to an otherwise boring landscape.

The garden is located at 660 South Cobb Drive where it intersects with Atlanta Road in Marietta. It is behind the Cobb County Water System’s building. The public is always welcome.

An excellent and easy to follow brochure is available called Rain Gardens for Home Landscapes. It will take you through the construction step by step. It includes the plants that are adapted to both wet and dry periods. You would only water this garden to get plants established. After that, the plants should be able to tolerate the extremes and still add interest to your landscape. Consider adding this low maintenance landscape feature to your yard and help protect water quality at the same time.

Resource(s): Landscape Plants for Georgia

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