|
|
||
 Selection of Site-specific Stabilization Techniques
Sloped banks are conducive to vegetation and to wildlife access to the water,
but the act of sloping the bank destroys riparian vegetation. If site-specific
wildlife access is critical, then some stabilization methods may require special
measures to provide access points.
Other terrestrial habitat measures may be separate from the protection work
itself, but may be appropriate as mitigation for the destruction of habitat due
to the work. Examples are erecting fallen trees as snags for nesting, feeding,
and perching sites for raptors or other birds, and creating artificial mounds for
bank-nesting birds such as swallows.
5.2.2.2 Avoid Disturbance of Endangered Fish and Wildlife
If endangered fish or wildlife are present in the vicinity of the project, avoiding
disturbance to them, especially during sensitive periods in their life cycle, may impose
constraints on the allowable construction period. Since some bank stabilization approaches
allow more flexibility in the timing and duration of construction than others, they are more
amenable to achieving this objective. For example, construction of a stone windrow on top
bank can be accomplished regardless of river stage, whereas a subaqueous armor usually
requires low to moderate river stages for successful construction. Therefore, choosing stone
windrow would provide more flexibility in the dates of construction.
5.2.2.3 Preserve or Improve Recreational Opportunities
One may view recreation as the link between objectives which are of vital concern to
nature, such as the quality of aquatic and terrestrial habitat, and objectives which are of
concern only to man, such as aesthetics and cultural resources. All of these influence the
quality of recreational activities such as boating, fishing, hiking, hunting, nature study, and
swimming.
However, easy and safe access to the stream for pedestrians, boats, or vehicles is a
separable factor in the quality of recreational activities, and thus can be clearly weighed in the
choice of a stabilization method. The method most amenable to suitable access is armor
accompanied by bank preparation in the form of sloping the bank. However, when
geotechnical stability is achieved by a wall of some type, then acceptable access may have to
be provided as a modification to the standard design. Special features, such as steps, walks,
access for the handicapped, fishing points, or boat launching facilities, can be justified in some
cases. The cost of such features may be minimal if incorporated into the design and
construction of the stabilization work.
Henderson and Shields (1984) suggest that stone dikes can be utilized as boat
launching points. However, swift and turbulent flow and sharp dropoffs into deep water are
likely to exist adjacent to the dikes, and if provision for boat launching is desirable, then the
106
1 6
|
||
|
||
