Rugged but artful dry streambeds can look as old as the hills, but they turn tricky drainage problems into handsome elements in any garden design.

Dry streams are really just above-ground drainage channels lined with rocks and placed to look as though nature had done the work herself. When it rains, water that would otherwise cut a muddy swath through a yard splashes along the stones in a streambed designed to handle the flow. When it's not raining, the dry streambed is a striking decorative feature, a rock garden around which plants naturally thrive.

"We got into it for the art of it," says Rodney Clemons of Rice and Clemons, an Atlanta company that specializes in dry streambeds, ponds and other garden stonework. "Then we started to see we could handle drainage problems without putting anything underground."

Gardens with slopes or even subtle changes in grade are good candidates for dry streambeds. Even if runoff is not a problem and the drainage is excellent, a streambed introduces a natural-looking topographic feature that shows water could have gone there at one time, Clemons says. Because they are made with rocks worn smooth by water, dry streambeds make even new gardens look well-established.

When Clemons and his partner, Thomas Rice, install a dry stream, they let the natural contours of the land define the bed and its width. In some gardens, such a stream might be only about 18 inches wide, Clemons says. In others, it might be up to 6 feet across.

The stream doesn't have to stretch the whole length of the property. A dry stream might trickle into or away from a pond in the garden or meander along a drainage line from a downspout through a garden bed. In a shady garden, a dry stream could emerge from a dense clutch of ferns and sweep out into the dappled light before disappearing again in the shrubbery.

Making a streambed requires a load of rocks and some imagination, but you don't have to have an engineering degree to do it yourself.

The best way to get ideas is to take a walk in nature, says Paula Refi, a garden designer in Atlanta. Think of a dry stream as a natural element of the landscape rather than as plumbing, she says. Studying the way real streams flow will give you ideas that translate -- with a little work -- into an effective feature in your own back yard.

Clemons and Rice like to hand-select the rocks for a job, and they visit several rock yards to pick and choose for their projects. "We like to use stones that are rounded, natural and old-looking, with moss and lichen," Clemons says. "We want stones that have character, but not too much. You don't want one stone to stand out any more than you want one plant to stand out."

Putting together a dry stream is like doing a puzzle, Clemons says. You need stones of various sizes: For a small stream, the small pieces will be about the size of a half-dollar, the larger stones as large as a basketball. A bigger project will involve larger stones, wheelbarrow-sized or even bigger (and heavier). Use stone of only one kind, Clemons suggests -- don't mix limestone, sandstone and granite, or the streambed will look contrived.

Before you place the first stone, you'll need to excavate to make sure the streambed is below the level of the lawn or bed around it. Then, place the largest stones first. The big stones should go at turns in the stream or where the grade drops, so it looks as though they have been exposed by the force of flowing water. Use smaller stones for the quiet places along the way.

To do it right, you can't really plan: You have to study the streambed as it develops and follow your instincts.

"There is an art to it," Clemons says. "It's easier for Thomas and me to put in a dry stream than it would be for someone just getting started, but it's still fun to do, if you're into sweating a little bit," he says. "You learn as you do it, and it's easy to change."

Making a dry streambed isn't really a weekend project. It takes time to design the streambed, find the rocks and place them artfully. Every stage of the project is gratifying, the experts say, so don't get in a hurry. Like making a garden, the rewards are long-lasting.

Doing it yourself

Stone experts have rock-moving equipment to handle the big stones required for large projects, but a wheelbarrow and a good garden spade should be all you need for a small streambed. Here are some tips.

* Don't be intimidated by working with stone, says Paula Refi, a garden designer. "This is not brain surgery. It's a simple concept."

* Choose your rocks carefully, looking for weathered stones. You may want to visit several stone yards and buy some rocks from each.

* Excavate sufficiently. A streambed should be below the existing grade. "The biggest mistake we see is people don't dig deep enough," says Rodney Clemons of Rice and Clemons in Atlanta.

* After a downpour, check the streambed. Heavy runoff may cause smaller stones to shift.

* If silt accumulates between the stones, that's just fine. It acts as natural grout.

* If possible, incorporate flat stones into the streambed, so you can step easily across your handiwork. "You want involvement," Clemons says. "We used to get upset with people and their kids when they would hop all over the rocks, but it's really a compliment."

* Every dry streambed will have a range of natural environments for plants. Borrow ideas from nature, Refi suggests, and use the wet and dry areas around the streambed for plants that prefer those situations.

Ferns, iris, native grasses, sedums and many other plants will work well on the margins of the streambed.