Drainage Solution: How to Build a Dry Streambed

A dry streambed or watercourse (also known as an arroyo can be built to direct water runoff away from your house foundation and toward areas where the water can percolate into the ground and irrigate plants. When designing your dry streambed, keep it natural and practical. Use local stone that’s arranged as it would be found in a natural stream. Take a field trip to an area containing natural streams and make some observations. Note how quickly the water depth drops at the outside of bends, where only larger stones can withstand the current. By the same token, note how gradually the water level drops at the inside of broad bends, where water movement is slow. Place smaller river-rock gravel here as though it had accumulated in a natural stream.

Large heavy stones with flat tops may serve as steppingstones, creating paths to cross or even follow dry stream beds.

The most important design principle for dry stream-beds is to avoid regularity. Stones are never spaced evenly in nature nor should they be in your streambed. Also, if you dig a bed with consistent width it will look like a canal or a drainage ditch, not a stream, so vary the width and the depth. Consider other yard elements and furnishings. For example, a dry streambed is essentially a river of rock. so it presents a nice opportunity to add a landscape bridge or two to your yard.

Contact your local building department before deliberately routing water toward a storm sewer; this maybe illegal. Before digging, call your local utilities hotline to have buried pipes and wires in or near the construction area flagged.

Tools & Materials:

Garden rake
Landscape fabric 6-mil black plastic ¾ to 2” river rock 6 to 18”- dia.
river-rock boulders
8-thick stepping stones Native grasses or other
perennials for banks

A dry streambed can be constructed to direct water runoff away from your basement walls and to add an attractive landscape feature to your yard.

Excavate the streambed to about 12’ deep, working within a no regular outline. The streambed should originate at a downspout from your gutter system. Follow the natural course of rainwater runoff where possible. End at a natural sink, such as a rain garden. Bends are often wider in natural streams, so make your stream wider at bends. Rake, smooth, and compact the soil within the project area.

Lay strips of landscape fabric over the excavation area, overlapping fabric by at least 12° at seams. Lay the fabric to within 2 to 3 ft. of the house, and then lay a strip of 6-m black plastic next to the house to direct water away and into the streambed. Weigh down the edges of the fabric with some of your larger rocks.

Place rocks in the streambed, beginning with larger boulders along the streambed banks. Extra excavation maybe needed to properly set extra large boulders. Fill around large boulders and line “rapids” with smaller boulders. You may also place stepping stones to make a pathway or bridge in an area where you’re likely to be walking. In most cases this feature is mostly ornamental.

Fill in spaces and create gravel bottoms with river rock in the ¾ to 2’ size range. Make sure the river rock you’re using is native to your area, and avoid dumping it all into a flat field. Retain some nice shapes and contours Trim off any exposed landscape fabric and plant native grasses and other perennials along the banks.