Contour Wattling

Description and Function

Contour wattling is an erosion control planting method which can also be used to stabilize very shallow soil structure against landsliding. The method involves packing lengths of woody plant material into cables or bundles (sometimes called live fascines) about 8 to 10 inches in diameter. The bundles are laid continuously along slope contours as shown in Figure 11. The cabling effect along the slope helps to intercept surface water runoff and route it laterally before it creates erosion problems. The wattles help trap sediment by creating barriers (living fences) to protect down slope areas against material falls or erosion.

Figure 11. Contour Wattling.

Planning Considerations

Woody plants which are particularly suitable to contour wattling are willow, red-osier dogwood, and snowberry. Wattling is generally considered good for slopes of 1.5H:1V or less. The installation of wattles along slopes requires a greater degree of planning prior to installation. Generally, wattles are placed horizontally in shallow trenches along preselected alignments on the slope at a single contour elevation. The wattles are placed into the trenches and partially covered creating what appear like slope terraces. Wattling installation along a slope face should progress from the slope toe upslope to the crest until planting is complete.

Figure 12. Wattle detail.

Wattles are created by laying plant materials length wise between two bucking horses (or modified saw-horses). Plant materials should be about 1/2 - 11/2 inches in diameter and about 4 to 8 feet in length. Butt ends and top ends are usually laid alternately until a bundle has been created that looks like an 8 to 10 inch wide cigar. Bundles are then tied together using untreated lengths of twine. This process is repeated until you fabricated the length of wattling necessary to finish a contour length. Next you live stake the downslope side of the trenches to hold the wattles in the trench overlapping the ends of bundles slightly. Place dead stakes (2 foot long section of a 2 x 4 stud cut diagonally) through the wattles every two feet. Finally, pull the soil from the trench excavation down into the wattles and compact into the trench by walking on the bundles. Make sure there is good soil-plant contact around and in the wattle.

About 80 percent of the wattle should be buried below the existing soil surface as shown in Figure 13. Leave the remaining area above the existing soil surface then cover with soil to intercept water and create mild slope terraces. At this time it is good to excavate the next upslope trench and then repeat the process. It is important to get the plant materials into the trenches before they have a chance to lose critical stem moisture. Seeding and mulching should follow immediately after installation.

Figure 13. Contour wattling detail.

Limitations

There is a significant quantity of plant material required for this technique. Installation is best performed with a labor crew of 3 to 4 people. The technique is time consuming if quality work is performed. For dry sites, summer watering maybe initially necessary.

Advantages and Disadvantages

  • Advantages: Good erosion control technique, can be used to manage mild gully erosion, can serve as slope drains when wattle cables are angled slightly.
  • Disadvantages: On steep or long slope lengths, high runoff velocities can undermine wattling near drainage channels, can dry out if not properly installed, covered, or maintained.

Applicability

Compatibility

Key to Applicability and Compatibility Graphics

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