Selection of Site-specific Stabilization Techniques
Robinson (1974). There is uncertainty over how much of the change is due to hydrologic
factors, and how much is man-induced, and further uncertainty over the roles of reservoirs,
changing land use, and river stabilization works, but it is certain that stabilization works had
a significant impact.
5.2.1.2 Terrestrial Wildlife Habitat
Impacts on terrestrial habitat may be more serious and longterm than is readily
apparent. The riparian zone is an extremely important component of an ecosystem, and the
ecological consequences of changes there may extend far beyond the immediate vicinity. It
provides the essential elements for diverse and productive plant communities (nutrients and
water) and for diverse and productive animal communities (food, water, and cover). The
riparian zone also serves as migration corridors between isolated pockets of natural habitat
in developed areas (Henderson and Shields, 1984). Terrestrial organic matter (vegetative
debris and insects) falling into the water is a source of energy for the aquatic ecosystem.
Construction activities may temporarily interrupt wildlife movement in the riparian
corridor, and interfere with normal breeding, nesting, and feeding. This is a serious, perhaps
unacceptable, impact if the species affected are rare or endangered.
5.2.1.3 Recreation
Recreation may be impacted both indirectly and directly, and favorably or unfavorably,
by a stabilization project. Stream-oriented recreation is indirectly affected by aesthetic,
aquatic, and terrestrial factors, such as naturalness of the surroundings, water quality, and
fishery quality. Potential direct impacts are related to safety and to ease of access to the
water. For some projects, particularly those in urban or recreation areas, safety will be an
important, even overriding, environmental factor. Judgement applied to specific site
conditions will usually adequately identify safety concerns, but consultation with a safety
specialist is well-advised if one is in doubt.
5.2.1.4 Aesthetics
Aesthetic impacts are subjective and intuitive, and are usually judged in the context
of the specific surroundings. Henderson (1986) suggests that aesthetic impact depends upon
the number of viewers, frequency of viewing, and the overall surroundings. For example, the
impact may be more important in urban or recreational areas than in an industrialized area,
but again this is subjective because an aesthetic setting may be rarer and thus of higher value
in an industrialized setting. Smardon (1983) discuss procedures for assessing aesthetic
impacts, while Gregory et al. (1992) provide evidence of the predictability of public response
to changing channel aesthetics with engineering of urban channels.
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