A Dry Streambed

Landscape Smart : Episode LDS-807 -- More Projects »
Our natural surroundings can often offer simple solutions to common landscape problems. If you have a drainage problem in your yard, a dry streambed is an attractive and natural-looking fix. And you can include a bit of artistry in how you place the stones.
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Figure A
Homeowners Bob and Debbie Siskin have a small backyard with a raised flagstone patio and lots of landscaping, but rainwater tends to puddle near the patio (figure A). Landscape designer Johan Kahlstrom designed a dry streambed, which provides a functional drainage system and a natural focal point with river-washed stones and boulders. A meandering course looks natural, slows the flow of water and creates pockets that are ideal for plantings.

Kahlstrom estimates that a professional would charge about $1,000 to design and install a streambed, but do-it-yourselfers can buy the stones and plants for about $250. This project is rated an easy 2 on a difficulty scale of 1 (easy) to 5 (difficult) and can be completed in one weekend.

Step One: Defining the Course

The site already has a natural grade leading away from the patio towards the side yard, which will help to funnel water to that area. This streambed will be 16 feet long.

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Figure B
Mark the course using landscapers' spray paint, starting where most of the pooling occurs. Mark a meandering course where you want the runoff to go. Vary the width of the stream from about 6 to 16 inches for a more natural look. Figure B shows the outline of the course.

Use a shovel to carve out the ditch, with the sides being concave rather than straight down. Gradually increase the depth from the sides to nine inches in the middle.

Step Two: Lining the Ditch

Landscape fabric, available for about $20 a roll, prevents weeds and helps hold the shape of the streambed. Cut one continuous piece of landscape fabric to the length and width of the streambed. Lay it in the bed and secure it with landscape staples or irrigation stakes. Smooth it out as you go to keep it taut. Pleat the fabric to shape it around curves.

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Figure C
Next, pour in a three-inch-deep layer of drain rocks (figure C) along the length of the stream. Then smooth a few inches of landscapers' sand on top for a more natural look.

Step Three: Placing the Boulders

Kahlstrom offers two key tips for creating a natural-looking streambed.

  • Vary the sizes of rocks and boulders to mimic nature.
  • Place bigger stones on the outer banks and medium and smaller stones towards the center.
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Figure D
He uses Napa wall rock (figure D), which is flat on top, to serve as stepping stones along the sides of the streambed.

Estimate where the stepping stones will go, marking out the distance of a normal stride, about 18 inches. Stagger the stones so that they don't line up too perfectly. After determining the placement, dig out a shallow trough underneath each one, and place them flat side up. Pack soil around the stones to keep them stabilized.

Create groupings of rocks along the outer edge, especially in the bends of the curves. Fill in along the edge with smaller rocks, placed randomly.

Step Four: Completing the Dry Stream

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Figure E
For the middle of the streambed, use river-washed stones and pebbles, such as a mixture of Sunburst and La Paz pebbles (figure E) for variety. Place larger stones towards the sides, and smaller ones in the middle. Sprinkle a layer of Olympic sand, available at landscape supply stores for about $8 per cubic foot, along the entire stream. It filters into the nooks and crannies to enhance the look of a dry streambed. Add pebbles to the middle of the streambed.

Use a hose to mist the streambed to push the clumps of sand into any gaps and around the stones so they'll appear to be embedded in the sand.

Planting: A Dry Streambed

Plants help to integrate the dry streambed with the surrounding landscaping. They also soften the edges and provide year-round color and interest. Kahlstrom recommends selecting plants that naturally occur along streams; he chose an assortment of grasses, lacy ferns, tall brushes, and flowering plants, including:

  • Cape rush (Chondropetalum tectorum), Zones 9-10
  • Phormium tenax 'Dark Delight', Zones 9-10
  • Autumn fern (Dryopteris erythrosora), Zones 6-9

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Figure F
The completed dry streambed (figure F) serves the dual purpose of solving a draining problem and adding a natural focal point to the yard. Although streambeds are low-maintenance, remove any twigs and leaves that get lodged between the rocks.
Guests
Johan Kahlstrom
Landscape Architect
The Avant Gardener
3871 20th St.
San Francisco, CA 94114
Phone: 415-824-0936
E-mail: avantgardener@aol.com
Website: www.avantgardener.org
Also in this Episode
Landscape Smart : Episode LDS-807
•A Dry Streambed