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Appendix B: Bioengineering for Streambank Erosion Control -- Guidelines
should be tied down with chicken wire or wire laced between stakes since the mulch may float
away when flooded (Edminster 1949).
Where severe erosion is expected and currents on the bank are expected to exceed 8 fps,
methods such as the brushmattress discussed for the splash zone above should be carried up
into the bank zone. Additionally, two other methods using woody materials are appropriate
for this zone. They include contour wattling and brush layering.
Contour Wattling. Contour wattling was discussed above as an integral component of
the brushmattress. In the bank zone, and in this context, it may be used independent of the
brushmattress along contours. Sometimes, you will see the term "fascine" in lieu of the term
wattling. They are buried across the slope, parallel or nearly parallel to the stream course,
and supported on the downhill side by stakes (Figures 39 a-c). They also have stakes driven
through the bundles and can be either living or constructed from wood as previously
described. The sprouting attributes of the brush species used, such as willow, combined with
the supportive attributes of the structure itself provide an integrated system of stems, roots,
wire, and stakes that hold the soil in place. When used on slopes, they protect against erosion
caused by downward water flow, wind action, trampling caused by wildlife and livestock, and
the forces of gravity. Further descriptions of wattling (fascine) construction can be found in
Edminster (1949), Schiechtl (1980), Gray and Leiser (1982), Allen and Klimas (1986),
Coppin and Richards (1990), and Georgia Soil and Water Conservation (1993).
Contour wattles (fascines) are often installed in combination with a coir fiber blanket over
seed and a straw mulch. In this way, slopes between the wattles may be held firmly in place
without development of rills or gullies. Figure 40 illustrates this and was prepared by Robbin
B. Sotir and Associates for the Corps of Engineers Nashville District and successfully used
on the Tennessee River near Knoxville, Tennessee. It should be noted that there was
significant toe protection in the toe zone with rock riprap; however, there was also overbank
flooding shortly after installation of the contour wattles and the treatment was stable.
Brush layering. Brush layering can be used in the bank zone as it was in the splash zone
except with some modifications. Geotextile fabrics, such as coir woven fabrics, should be
used between the layers and keyed into each branch layer trench, so that unraveling of the
bank does not occur between the layers (Figure 41). Before the geotextile fabric is applied,
the areas between the branch layers should be seeded with flood-tolerant grasses or grass-like
plants, like sedges, and then covered with a straw mulch. This method was used to stabilize
levees in low-lying areas of fen districts in England (from Gray and Leiser, 1982 who cited
Doran, 1948). Slope heights, the vertical distance between the layers, should not exceed 3
times the length of the longest brush in the trench. This would be similar in principle to a
sloping reinforced earth revetment (from Gray and Leiser, 1982 who cited Bartos, 1979)
where metal strips are placed essentially horizontally in successive layers up the face of a
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