VEGETATIVE METHODS FOR EROSION PROTECTION
The two previous chapters addressed structural approaches to erosion protection, in
the form of surface armor and indirect techniques. Vegetation's great potential for use in
erosion protection, and the requirement that it be carefully planned and designed using skills
not usually included in traditional engineering knowledge, merits separate discussion. This
chapter is not an exhaustive treatment, but does present a rational overview of the subject.
The latest U.S. Army Corps of Engineers guidance for bioengineering for streambank erosion
control is discussed in Appendix B.
Vegetation is the basic component of what is known as "bioengineering" (Schiechtl
1980) or biotechnical engineering (Gray and Leiser, 1982; Gray and Sotir, 1996). Schiechtl
(1980) states that bioengineering requires "the skills of the engineer, the learning of the
biologist, and the artistry of the landscape architect." The concept of bioengineering is
ancient, but there has been much recent research and documentation of the topic. The
publications just cited, as well as Coppin and Richards (1990), provide comprehensive
coverage, and many other works provide discussion of specialized aspects of the subject.
9.1.1 FUNDAMENTAL CONCEPTS
Vegetation can function as either armor or indirect protection, and in some
applications, can function as both simultaneously. Grassy vegetation and the roots of brushy
and woody vegetation function as armor, while brushy and woody vegetation function as
indirect protection. The roots of vegetation may also add a degree of geotechnical stability
to a bank slope through reinforcing the soil.
Some factors which affect the success of a bioengineering approach, such as weather
and the timing and magnitude of streamflows, are beyond the designer's control. Therefore,
expert advice, careful planning, and attention to detail are critical to maximizing the
probability of success.