Criteria for the Depths of Dredged Navigational Channels (1983) / Chapter Skim
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Appendix B: Selection from Engineer Manual, 'Channel Depths'
Appendix B: Selection from Engineer Manual, 'Channel Depths'
Pages 145-150
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From page 145... ...
The design depth of the channel will be premised upon the drafts of the design vessel while in motion, including the effect of squat, rolling, and pitching; plus a nominal clearance of 2 or more feet; plus an allowance for frequent low tides that are below mean lo`v water, when vessel delay is uneconomical, or minus an allowance for some stage above mean low water when the resulting delay of vessels is not uneconomic. Consideration will be Wren to the provision of greater depths than those required for safe navigation, as determined by the foregoing considerations, when it can be shown that the reduced power required to propel the vessel at a maximum safe speed at the greater depths produces savings commensurate with the costs of providing the greater depths.
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From page 146... ...
be those considered to be normal for the particular operations of the design tresses in the channel under consideration. The static draft of a ship is usually stated with reference to its flotation in "summer salt water." In passing from sea water of normal ocean salinity to fresh water, a ship having a static draft of 35 feet in sea water at lS degrees centigrade (density 1.026)
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From page 147... ...
In waterways where the selected plane of reference for providing the design depths varies significantly in absolute elevation from reach to reach, the waterway should be sectionalized and a separate datum used for each section rather than a single datum for the entire waterway. In some cases, local mean low water is as much an a foot higher in the upstream reaches as compared with the lower sections.
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From page 148... ...
It is noteworthy, that the channel alignments of important existing projects in the United States are often inferior to those proposed by the Panama Canal engineers. In brief, if curves must be used, the best practice will be to lay out the channel with the maxima radii and the minima deflection angles, and the maximum tangent distances that the physical conditions permit, without incurring excessive first or annual costs.
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From page 149... ...
While channel width and channel depth are factors of equal significance insofar as cross sectional area is concerned, it appears that inadequate depths are much more hazardous than inadequate widths, and they cause greater delay to vessels. On the other liand, a choice between Lie provision of a channel of width adequate ~ permit two-way traffic and inadequate depths at low tide, as compared with a channel suitable for one-way traffic of design vessels and of adequate depth even at low tide, must take cognizance of the possibility that the greater depth may cause a shift in the location of the bulk of the shoaling.
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From page 150... ...
In the event it is found that a channel modification of the nature most desirable for navigation will have adverse effects on the quality of the water and hence on its value as a source of water supply, further study may consider possible reductions of the dimensions and/or extent of the channel, barriers to exclude salinity', upland reservoirs to enhance low fresh water flows, or the provision of an alternative source of water supply to replace the tidal waterway as a source of water supply.
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