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 Selection of Site-specific Stabilization Techniques
proposed stabilization approach changes existing channel alignment and
geometry, the less complex the potential project-induced changes. If the
project will change channel alignment or geometry significantly, or if local
interests are likely to be concerned about the impacts of even a simple project,
then an expert geomorphic and hydraulic analysis is advisable.
5.2 ENVIRONMENTAL CONSIDERATIONS
This section builds upon the broad environmental concepts discussed in 4.2.2. Here
we address more tangible factors which influence the selection of a method to solve a site-
specific riverbank stability problem.
The ultimate evaluation of the success or failure of some bank stabilization projects
may rest on their environmental impacts, because environmental impacts are often judged by
a much wider audience than is the project's success as bank stabilization. The weight of
public opinion may be unfavorable even if the project is completely effective as bank
stabilization.
In spite of many examples to the contrary, bank stabilization projects can effectively
address environmental concerns. Because many river engineers and scientists are
"environmentalists," and many "environmentalists" recognize the need for riverbank
stabilization, progress has been made in transforming the attitude of environmental awareness
groups from one of automatic resistance to any river modification, into one of cooperation
and dialogue in the development of improved environmental features for incorporation into
necessary bank stabilization projects. The selection phase provides more opportunity for this
cooperation than does the design stage; therefore, effort expended at this point will provide
significant returns.
Environmental considerations and opportunities can be analyzed in the following
order:
Potential environmental impacts;
Environmental objectives; and
Identification of environmentally preferable methods.
5.2.1 POTENTIAL ENVIRONMENTAL IMPACTS
The difficulty of defining potential environmental impacts of a bank stabilization
project is illustrated by the following two scenarios:
Armor protection usually requires bank preparation. This will destroy some
vegetation on or near the streambank, although if the bank was eroding, then
the bank vegetation would have been destroyed by the erosion anyway. If the
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