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 Appendix B: Bioengineering for Streambank Erosion Control -- Guidelines
Care should be taken, however, to ensure the upstream end is not flanked by
currents, thus possibly jeopardizing that bank reach.
The dormant post method using willow provides a low-cost bank stabilization method
with both wildlife and fisheries benefits. Roseboom (1993) reported that the method has
received widespread support by both the agricultural and environmental communities: Farm
Bureau, Soil and Water Conservation Districts, American Fisheries Society, and the Nature
Conservancy. The willows hold the soil together long enough for other plants to become
established on the bank through succession. Together, they provide a natural system of food
and cover. More can be found on this method in the case study provided in Volume II.
Dormant Cuttings. Dormant cuttings, sometimes called "Live Stakes," involves the
insertion and tamping of live, rootable cuttings into the ground or sometimes geotextile
substrate. In higher velocity streams, such as over 5 fps, this method usually is applied in the
splash zone with a combination of other methods, such as the brushmattress and root wad
methods. Dormant cuttings can be used as live stakes in the brushmattress and wattling as
opposed to or in combination with the wedge-shaped construction stakes previously
mentioned. Or, they can be placed adjacent to the brushmattress. They can also be used in
the matrix openings of the root wad logs along with root pads of other vegetative materials.
If cuttings are used alone in the splash zone, the toe should be very stable and velocities
should be less than 5 fps. Also, the soil in which they are placed should be fairly cohesive.
Figures 37 a-c show an application of bankers (Salix X cotteti) and streamco (S. purpurea
'streamco') willow cuttings that was installed on Irish creek in North Carolina by the NRCS.
These willow were installed on a fairly cohesive bank on a staight reach with a stable toe.
Dormant cuttings can vary in size, but are usually a minimum of 1/2 inch in diameter at
the basal end (Hoag, 1994b). Cuttings can be used that are up to 2 to 3 inches in diameter
and have been noted by Hoag (1993) to have the highest survival rates. Cutting length is
largely determined by the depth to the mid-summer water table and erosive force of the
stream at the planting site (Hoag 1993). Plantings can occur at the water line as in the splash
zone, up the bank into the bank zone, and on top of the bank (terrace zone) in relatively dry
soil, as long as cuttings are long enough to reach into the mid-summer water table (Hoag
1993).
Cuttings should have their side branches cleanly removed and the bark intact so that the
cutting is one single stem. Care should be taken to make clean cuts at the top and the bottom
so that the bark is not separated from the underlying woody tissue. Also, be sure they are cut
so that a terminal bud scar is within 1 to 4 inches of the top because cuttings put out their
greatest concentration of shoots and their strongest ones just below an annual ring (formed
from a terminal bud scar). At least two buds and/or bud scars should be above the ground
after planting (Gray and Leiser, 1982). Tops are normally cut off square so they can be
tamped or pushed easily into the substrate. The basal ends are often angled for easy insertion
into the soil. When selecting material from a natural stand, care should be taken to see that
the harvest material is free from insect damage, disease, and splitting.
B-57
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