CHAPTER 4
GENERAL APPROACH TO BANK STABILIZATION
This chapter forms the link between the analysis of channel stability and the selection
of appropriate solutions to problems of bank retreat.
"Complex problems often have quick and simple wrong answers" is an apt epigram
for problems of riverbank stabilization. River engineers and scientists may be pressured by
circumstances beyond their control to plan and construct riverbank stabilization works too
quickly, without adequate time or resources for a conceptual evaluation of the problem. The
immediate need may be perceived as award of a construction contract when the immediate
need may, in reality, be a sound stability analysis of the channel system. The pressure to
proceed prematurely to construction should be resisted with logic, while still recognizing that
there are practical constraints on data collection and analysis, and that there is often a genuine
need for timely corrective action. River scientists and engineers have the privilege and duty
to educate the public, representatives of the public, project sponsors, and project managers
about river characteristics, and especially the response of rivers to human modification. It
must be pointed out that mistakes in detailed design may be only mildly embarrassing and
easily correctable, but that mistaking the cause or degree of instability at the outset may doom
the entire project to eventual failure.
A more positive perspective is that a system analysis may also identify significant
potential benefits from bank stabilization works that might otherwise be neglected. Examples
of such benefits are improved water quality and reduction of downstream sedimentation
problems. Such benefits are difficult to quantify, and are likely to be achieved only by
comprehensive projects, but should be recognized.
Sometimes the obviousness of the bank failure mechanisms obscures the more
important underlying causes of bank failure. Without having had either the misfortune of
making serious mistakes, or the less traumatic experience of merely observing them, a person
may be prone to oversimplify the causes of bank retreat, because a river may take decades to
react to imposed changes. Also, the causes and effects of changes are inter-related through
complex response. Therefore, the more experienced the observer, usually the more cautious
he or she is about making initial judgements.
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