Regrading is acceptable, as the land is undeveloped, so revetments are a possibility. Little useable
land would be lost in this case because of the low bluff height. A rubble revetment is a likely alternative
because stone is available in the area at a reasonable price. A typical design will be shown. Concrete
blocks would also be applicable. The steps involved in designing concrete block and stone revetments
are similar and therefore will not be repeated, but in a real design, the comparative costs of stone and
concrete block revetments should be developed. Stacked bags and mats were eliminated for aesthetic
reasons and because of short life expectancy when exposed to water-borne debris and bombardment by
stones and cobbles. Gabions were also judged to be too short-lived in this situation. Materials for fuel
barrel and concrete slab revetments were unavailable.
A breakwater does not provide positive protection to the bluff toe. To avoid downdrift erosion
problems, sand would have to be imported from a borrow area nearby. This would require additional
expense and would still not provide positive toe protection. Therefore, all breakwaters were eliminated.
Groins were also rejected for the same reasons.
A beach fill and a perched beach were considered as possibilities because the offshore slope is
mild. However, they do not positively protect the bluff toe and enhanced recreational use of shoreline
was not a high priority of the owner. Because neither would provide the needed protection, they were
not selected as possible alternatives. Slope flattening or infiltration and drainage controls were
inappropriate. Slope flattening, however, would be a part of the revetment design and proper
Vegetation, if used alone, would be ineffective. Completion of the Vegetation Stabilization Site
Evaluation Form (Figure 28) yields a score of 32, which places the site just beyond the acceptable range.
One possible combination approach will be developed that employs devices that were rejected
when considered alone: a gabion revetment, a perched beach retained by a sand bag sill, and vegetation.
The vegetation will provide a buffer zone to inhibit wave action against the bluff toe. The existing gravel
beach will not support plantings so the perched sand beach and sill are provided to encourage plant
growth while also protecting the new plantings against wave action. A recomputation of the Evaluation
Form (Figure 28), with a perched beach of medium sand, yields a score of 28, which is in the acceptable
range.
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