Runup Calculation. From Table 4. with the design wave height,
H = 4.0 feet for a vertical face
R = 2.0 H = 2.0 x 4.0 = 8.0 feet
The design top of structure is at the crest of the bluff, or +9 feet MLW. The runup above the design
Stillwater level would be to +11.6 feet MLW (8.01 + 3.61 ). The structure, therefore, will be overtopped
during design conditions, and a splash apron must be provided at the crest.
Backfill. Only granular backfill material should be used. The fall must be placed and compacted
around the deadmen before any is placed behind the wall. Otherwise, load would be applied to the wall
without support of the anchoring system and failure could result.
Filter Cloth. A continuous filter cloth is provided behind the planks and under the overtopping
apron. It is needed to prevent the backfill and natural bluff material from being washed out. Additional
holes in the wall were not included in the design because the small spacing between the planks will
provide sufficient drainage.
Toe Protection. Toe protection is provided to insure stability against scour. A filter cloth is used
to prevent settlement of the rock. Given a unit weight of stone, w = 165 lbs/ft and a design wave height,
H = 4.0 feet; from Tables B-1, B-2 and B-3 (APPENDIX B), find the required stone weight, W.
From Table B-1, with H = 4.0 feet, W = 390 pounds.
The toe protection is placed on an essentially flat surface so enter Table B-2 with the flattest slope shown
(1:6) to correct W.
From Table B-2, for a 1 on 6 slope (1:6), the correction factor, K1= 0.3. Therefore,
W = 390 x 0.3 = 120 pounds
The range of allowable stone weights is 0.75W to 1.25W with 75% greater than W, therefore,
wmin =0.75 x 120 = 90 pounds
wmax =1.25 x 120 = 150 pounds
Seventy-five percent should exceed 120 pounds and no stone should be accepted if the longest dimension
is more than three times the shortest.
Flanking. The bulkhead will be tied into the existing bluff.
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