Properly handling runoff can turn wet areas into landscape highlights

It seems that we can't ever be satisfied. For most of this year, we have been begging for rain. Now, we need the soil to dry out some.

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When we get wet conditions, I start getting a lot of calls on how to correct wet areas. There are some simple solutions and there are solutions that take more time and money.

The most common water problem in Columbia County is runoff. Improperly channeled, runoff will cause damage to your property.

It is important to note the elevation of your property in relation to adjacent properties. Does the land slope? Where will rain water come from, and what is in its path? During a rainstorm, watch to see where runoff flows and exits. Ideally, your home will have sufficient outlets to handle rooftop, driveway and overland runoff.

Erosion due to runoff coming from higher elevations is the most common water problem faced by homeowners. The problem is most obvious and most damaging when you live downhill from a number of properties.

If the majority of the run-off is coming from your roof, you can pipe the water to a low-impact location such as a drainage easement, a creek or the street. Downspout fittings can be purchased at a home supply store and used to pipe the water to the low-impact area. Avoid sags in the pipe to ensure downhill flow. This might mean burying the pipe to give it enough fall. Always ensure that the outlet is open and clear of debris.

If you are unable to pipe the runoff from the site, a swale or diversion may be a solution. A swale is a broad depression that can be constructed to transport water more directly.

A swale should be at least 3 feet wide across the top and at least 6 inches deep. Be sure the swale has enough downhill slope to prevent ponding. The surface should be sodded with grass for protection. Occasionally flat rocks are necessary to protect large swale surfaces from erosion. Rock may also be placed at the outlet to disperse the force of the water. Swales should drain into a creek, drainage easement, street or wooded area.

Another solution that is becoming popular is the use of rain gardens. The idea behind rain gardens is to capture the water that runs across your landscape to use in a specific area to grow plants. Again, the first step is to find the direction of the water flow.

Next, determine how large the rain garden needs to be by measuring the roof area in square feet. If your roof is 60 feet by 30 feet, you have 1,800 square feet. Now, figure in a rainfall event. In Georgia, 80 percent of the rain we receive will be 1.25 inches or less. So multiply 1,800 square feet by 1.25 inches or .104 feet, This will give the cubic feet of water. In my example, you will have 187 cubic feet of water.

So, you have to figure out a bed that will come close to matching 187 cubic feet. A bed that is 10 feet wide, 12 feet long and 18 inches deep will give you 180 cubic feet. Then, perform a percolation test on the soil to see if the soil drains properly. Dig a hole at least 1 foot deep and fill it with water. If the water doesn't drain in 24 hours, loosen the soil and add small rock or fine ground pine bark to aid with the drainage.

Once this is done, amend the soil with compost and have a soil test done to see if the soil needs lime. The top of the soil should be within 1 inch of the top of the rain garden. Take the extra soil and make a berm on the downhill side of the rain garden. The next step is to plant your plants.

There are trees, shrubs and perennials that can be planted in the rain garden. Some of the trees that do well are Bald Cypress, Black gum (Nyssa sylvatica), River Birch and Red Maple. These trees will grow in full sun or partial shade. The bald cypress will send up cypress knees from its root system, so it is not good in the middle of your landscape.

Some of the better shrubs to plant are Bottlebrush buckeye, Florida Anise, Sweetshrub, wax myrtle and winterberry. These plants like to grow in partial shade. There are other shrubs that can grow in full sun.

There is a range of perennials and bulbs that can grow in rain gardens. Some good plants are Astilbe, calla and canna lilies, elephant's ear, Japanese and Louisiana iris and swamp sunflower.

Columbia County Extension Agent Charles Phillips can be reached at (706) 868-3413 or by e-mail at charlesp@uga.edu. The Extension Web address is www.ugaextension.com/columbia.