12 December 2001
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.
Defining Fleet Requirements.
All dredging activities must be coordinated with the NAVFAC Criteria
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.
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
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