UFC 4-150-06
12 December 2001
5-6.2
Development of a Navigation Project. Often a navigation project
requires one or more engineered structures to accomplish its objectives. Structures
can serve a variety of purposes. However, their presence also establishes a major
hazard for vessels. Hence, a navigation structure must be designed with regard to
several functional concerns. Basic types of structures and functions involved in
navigation projects are briefly discussed in CEM Section V-5. Sediment processes and
management at inlets and harbors are discussed in CEM Section V-6. Detailed
guidance on structure design is given in CEM Section VI.
5-6.2.1
Defining Fleet Requirements.
All dredging activities must be coordinated with the NAVFAC Criteria
Office.
The activity should coordinate the following issues with the major
claimant: classes of ships used at the facility, access frequency, days of
harbor access required, and function performed in the harbor,
Most harbors cannot design for 100% accessibility, so the amount of risk
the claimancy wants to take on should be addressed.
Seakeeping issues in the channel shall also be addressed.
Check for criteria of thickness of ice; refer to paragraph 5-5.1.11, Ice
Loading, for references.
5-6.2.2
Entrance Channel Configuration. Designing approach-channel and
entrance-channel widths for harbors located in exposed ocean-wave environments is
largely accomplished by comparing presently operating harbors. The forces of waves
and currents acting on a vessel in exposed locations induce excursions of the vessel
from its intended path of travel. For example, to pass in the lee of an entrance
structure, a vessel needs maneuvering room in order to adjust to the rapid changes in
sea conditions.
Where naval activities share common entrance approaches with
commercial port activities, entrance-channel widths greater than 304.8 m (1,000 ft) are
common. Table 5-7 gives entrance-channel dimensions for several typical harbors.
Table 5-8 provides typical harbor entrances serving naval facilities.
For new entrance designs, preliminary width approximations can be made
as given in paragraph 5-6.2.2c, Entrance Channels, by adjusting ship beam with yaw
angle increase and then proceeding as for an interior-channel design. In the case
where the hydraulic environment at the entrance is unique and without precedent,
navigational studies involving suitable-scale physical model methods are
recommended.
5-42
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