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 General Principles of Erosion Protection
stabilization methods, one or more factors can be quickly dismissed. For example, provision
for surface drainage is not usually required for "indirect" protection methods, while
manufacturer's recommendations apply only to commercial products.
At this point, a caveat which has been inferred previously in Chapters 4 and 5 must
be reiterated: to arrive at the point of designing a site-specific bank stabilization project, the
designer must make one of the following judgements:
that the fluvial system is in equilibrium;
that system instability exists, but that channel changes will not significantly
affect the bank stabilization project, or that the bank stabilization can be
designed to accommodate such changes; or
that system instability exists, but that it will be corrected in conjunction with
site-specific bank stabilization if appropriate.
In practice, the problem of making an assumption regarding system instability is not
as difficult as might first be imagined. In practice, the first two conditions often apply, and
successful bank stabilization projects have been built without the designers taking into
account the possibility of system instability. Ideally, however, any element of chance can be
removed from project design by first applying the principles discussed in Chapters 2 and 3 to
correctly determine the causes and mechanisms of bank retreat.
6.1 APPLIED GEOMORPHOLOGY
This section deals with the integration of the understanding of stream characteristics
outlined in Chapters 2 through 3 into the decision-making process with regard to the location
of bank stabilization works. The specific aim is to describe how best to use "applied fluvial
geomorphology" to make the following two basic decisions:
Location of the upstream and downstream limits of work
Alignment of the work with respect to the stream channel
6.1.1 UPSTREAM AND DOWNSTREAM LIMITS OF WORK
This initial design decision is based on an analysis of channel migration, a
consideration of the minimum requirement for length of bank to be protected, and other
detailed considerations.
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