Navigation General · Tides
A vessel drawing 20 feet approaches a harbor entrance. The chart shows 16 feet at the entrance (MLLW). Predicted low water at the entrance is 1.5 feet above MLLW and high water is 7.5 feet above MLLW. What is the minimum height of tide above MLLW required for the vessel to enter with 2 feet of clearance?
- A4.0 feet
- B5.5 feet
- C4.5 feet
- D6.0 feet✓ Correct
Explanation
Required depth = draft + clearance = 20 + 2 = 22 feet. Charted depth = 16 feet. Required height of tide above MLLW = 22 − 16 = 6.0 feet. The tide must be at least 6.0 feet above MLLW for safe entry.
Authority: NOAA Tide Tables; Bowditch (Pub. 9), Ch. 9
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