|
|
||
 General Approach to Bank Stabilization
4.1.5 NON-STRUCTURAL SOLUTIONS
Two situations where a non-structural alternative may be considered are:
Erosion due to navigation traffic in confined channels
Bank instability caused by varying reservoir releases
4.1.5.1 Regulation of Navigation
Regulation of vessel size and speed to reduce erosion from boat or ship passage is a
preferable solution and has major environmental benefits, but it may be legally or politically
impractical, depending on the local situation. Prediction of the reduction in erosion from
regulation is also difficult, which compounds the legal and political problem. Also, public
perception of the cause of erosion tends to overemphasize the actual effects of vessel traffic.
4.1.5.2 Regulation of Reservoir Releases
This approach presents much similar benefits and problems as regulation of
navigation. Reservoir releases are usually dictated by multiple purposes, and their impact on
bank stability is likely to be well down the list of priorities. Also, the public perception of
damages from reservoir operation may far exceed the actual damages. In fact, as discussed
in Section 4.1.1.2, the net effect of reservoirs is often to improve bank stability. Two
exceptions may exist:
If discharge from a reservoir is frequently and rapidly reduced from close to
bankfull to no flow or low flow, geotechnical instability may be increased
compared to natural conditions.
If reservoir operation increases the duration of high in-bank flows, the total
amount of bank erosion associated with those flows will obviously increase.
However, an increase in long-term erosion will be difficult to prove, because
the accompanying reduction in peak flows and their associated erosion may
more than compensate.
4.2 CONSIDERATION OF OTHER FACTORS
A project which performs adequately by traditional engineering standards can
nevertheless create public dissatisfaction, because the public takes good engineering for
granted, and sometimes focuses on the project's negative aspects. This negative focus may
result from inadequate consideration by the project planners of factors which may be beyond
what is traditionally considered to be included in the engineering of a project.
9
79
|
||
|
||
