Georgia Gardener Newsletter Design Tip

Georgia Gardener Newsletter Design Tip: May 18, 2006

Dry Streambeds

Functional and aesthetic. Whether you have a drainage problem or not, a dry streambed can add the "appearance" of water to your garden. This design concept was borrowed from Japanese gardens and has definitely "caught on" in America.

Erosion Control

If your landscape suffers from torrents of water that occur after a heavy rainfall but is dry the rest of the time, a dry streambed can be used to channel the water through the landscape thus reducing erosion and damage. Construction of a dry streambed for this purpose will be different than if it is simply an ornamental feature.

First, determine the course the water takes. This is often very simple as the grass will be bare, soil will be missing or the mulch will be pushed aside. If the runoff is severe enough to have already begun to dig a channel, that will make the job easier. If at all possible, follow the course of the water. If you must change the water's direction, you will probably need to dig the dry streambed slightly deeper and wider at the turns. Make gentle sloping turns as rushing water has great force and determination.

Dig the channel larger than will be needed to handle the runoff. The depth and width needed will be dependent upon the overall size of the streambed as well as the volume of water. The bottom and sides of the streambed should be line with landscape fabric to help prevent weeds and to maintain the shape of the streambed. Hold the landscape fabric in place with rocks of varying sizes from boulders to pebbles. For a natural look, use river rock. Make sure that the landscape fabric is completely hidden from view.

Note: If you have a heavy runoff or if the water rushes quickly, you will need to have large rocks. Water exerts a tremendous amount of force which can easily wash smaller rocks to the end of your streambed.

After every heavy rain, make sure that your streambed is free of debris or you could experience a "back up" during the next downpour. It's also advisable to keep leaves and mulch from building up as it may impede the flow of the water and hide the beautiful rocks from view.

Decorative Feature

If the purpose of your dry streambed is purely aesthetic, then you can make the direction and size to your liking. I would still dig the dry streambed to be below the grade of the rest of the garden and line it with landscape fabric. However, you can use smaller rocks and even decomposed granite at the bottom to simulate water.

Landscaping

A drystream bed that runs through the lawn or other bare area may look out of place. I prefer to incorporate plantings to soften the appearance and give it a more natural look. I also like to avoid using shrubs that have a formal appearance such as pruned boxwoods or hollies.

If your streambed is in sun, use plants that have a weeping or arching growth habit such as Gold Mop Chamaecyparis and Virginia Sweetspire (Itea). Ornamental grasses such as Muhly Grass will also soften the edges. Finally, a low-growing preferrably evergreen ground cover at the top edge that can work its way through some of the rocks will look fantastic.

The same design principles will apply to streambeds in shade. Plantings can include Hostas, Ferns, Anise (Illicium), Azaleas, Rhododendrons and Doghobble (Leucothoe).

For more information on dry streambeds, visit this website.