Fetch Line 1 with F = 3.2 mi and WS = 65 mph:
Table 6: d = 10 ft; H = 3.0 ft; T= 4.0 sec
Table 7: d = 15 ft; H = 4.0 ft; T= 4.0 sec
Fetch Line 2 with F= 2.4 mi and WS = 65 mph:
Table 6: d = 15 ft; H = 3.5 ft; T= 4.0 sec
Table 7: d = 20 ft; H = 4.0 ft; T= 4.0 sec
Therefore, by interpolating for d = 10.8 ft; H = 3.2 ft; amd T = 4.0 sec.
Fetch line 2 is more critical for design. Therefore, use H= 3.5 ft and T = 4.0 sec.
This value should be checked against the maximum breaking wave at the site or just offshore. (Recall
that Fetch Line 1 crosses a shoal area near cedar point where the depth is approximately 3 feet under the design
Stillwater level. Fetch Line 2, however, was more critical for design purposes). With the design Stillwater
condition, the depth at the bluff toe, ds = 3.2 feet (Figure 90).
From Figure 18 with,
Ds/gT2 = (3.1)/32.2 (4.0)2 = 0.0060,
and m = 0.03, Hb/ds = 0.98
Therefore, Hb = 3.1 x 0.98 = 3.0 ft.
Therefore, for shoreline protection, use a design wave height of 3.0 ft, because that is the maximum that
can occur at the site under design water level conditions. For any offshore structures, such as breakwaters or
perched beach sills, the maximum breaker height should be checked based on design depth at the toe of the
structure.
SELECTION OF DEVICES
Landowner's Criteria
1. No recreational use of the beach for bathing or fishing is anticipated.
2. The owner eventually hopes to extend an existing dock to deeper water for berthing a pleasure
boat.
3. No structures are planned at eh top of the bluff that would interfere with any shore protection
devices.
4. The shore protection plan should provide about 10 years of protection with minimal maintenance
requirements.
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