Appendix B: Bioengineering for Streambank Erosion Control -- Guidelines
Assets of Using Planted Vegetation
Gray (1977), Bailey and Copeland (1961), and Allen (1978) discuss five mechanisms
through which vegetation can aid erosion control: reinforce soil through roots (Gray, 1977);
dampen waves or dissipate wave energy; intercept water; enhance water infiltration; and
deplete soil water by uptake and transpiration. Klingman and Bradley (1976) point out four
specific ways vegetation can protect streambanks. First, the root system helps hold the soil
together and increases the overall bank stability by its binding network structure, i.e., the
ability of roots to hold soil particles together. Second, the exposed vegetation (stalks, stems,
branches, and foliage) can increase the resistance to flow and reduce the local flow velocities,
causing the flow to dissipate energy against the deforming plant rather than the soil. Third,
the vegetation acts as a buffer against the abrasive effect of transported materials. Fourth,
close growing vegetation can induce sediment deposition by causing zones of slow velocity
and low shear stress near the bank, allowing coarse sediments to deposit. Vegetation is also
often less expensive than most structural methods, it improves the conditions for fisheries and
wildlife, improves water quality, and can protect cultural/archeological resources.
Limitations of Using Planted Vegetation
Using planted vegetation for streambank erosion control also has limitations. These may
include its occasional failure to grow; it is subject to undermining; it may be uprooted by
wind, water, and the freezing and thawing of ice; wildlife or livestock may feed upon and
depredate it; and it may require some maintenance. Most of these limitations, such as
undermining, uprooting by freezing and thawing, etc., can often be lessened or prevented by
use of bioengineering measures.
B-5
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