Criteria for the Depths of Dredged Navigational Channels (1983) / Chapter Skim
Currently Skimming:
Evaluating the Adequacy of Criteria for Dredged Depths of Navigational Channels
Evaluating the Adequacy of Criteria for Dredged Depths of Navigational Channels
Pages 85-106
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 85... ...
The results of the simulation are presented in the succeeding section, followed by the criteria of international organizations, foreign maritime countries, and shippers. Dredged Depths of Navigational Channels in the Uhited States Navigation The criteria used to design the depths of navigational channels in the United States are described in Chapter 2, "Regulatory and Institutional Considerations." For the major channels of the United States, the pertinence of the design ships used for the original 4-l
|
From page 86... ...
Chesapeake and Delaware Canal 4. Calcasi eu River Speed Limit Assumed 5 kn 6 kn 6 kn 6 kn From the panel's observations and brief ings during f held trips, the assumptions -- including the design ships -- are conservative.
|
From page 89... ...
~ ~ . Criteria of International Organizations, Other Maritime Countries, Shippers Criteria of International Organizations PIANC Criteria In 1974, the Permanent International Association of Navigation Congresses ( PIANC ~ sponsored an International Commission for the Reception of Large Ships ~ ICORELS ~ .
|
From page 90... ...
~ Figure 37] shows the def inition of underkeel clearances used by the Commission in their recommendations and are described as follows Lsection 2.2.2.41: THE GROSS UNDERKEEL CLEARANCE is by definition the margin between the keel of a vessel and the nominal channel bed level, considering the water ref erence level during its pas sage and the maximum draught of the vessel, measured at rest in calm water.
|
From page 91... ...
- 9.d level } Figure 37 Underkeel clearances as defined by PIANC Permanent International Association of Navigation Congresse * SOURCE: COLS (Committee on Large Ships)
|
From page 92... ...
the increase in ef f ective draught due to the rolling, pitching and heaving of the ship under wave action within the channe 1, * the estimated squat and change of trim f or the design ship calculated f or each critical depth area based on the maximum Fermi ssible operating ship speed and the most constricted channel section within the critical depth area, The normal loaded condition of the design ship and *
|
From page 93... ...
The code outlines acceptable ship terminal standards, def ines the required ship terminal system analysis and assessment criteria, and sets out operating practices and procedures for ship terminals. Although published by the Canadian Coast Guard, the TERMPOL code is a coordination and correlation or the separate requirements of the Canadian Department of Fisheries and the Environment, Public Works, And -m, and Reg~ona-l and Economic Expansion.
|
From page 94... ...
and for that of dredging processes; o Incidence and degree of channel silting between maintenance dredgings and the identif ication of all critical depth areas; 0 Increase in effective draft due to the rolling, pitching, and heaving of the ship under wave action within the ship channel; o Estimated squat for the design ship calculated for each ~rit~ ; Moth - treat based ~a - anal maximum' per=rse~peret~ns ship speed and the most constricted channel section within the critical depth area; o Nominal trim and changes of trim experienced by the design ship; o Draft and trim changes attributed to any changes in water density; 0 Climatological and related depth anomalies; and 0 Nature of the bottom (rock, sand, mud, etc.
|
From page 95... ...
: DEPTH OF BASIN 1 ) The depth of basin shall be 1.1 times full load draft of the ship below the datum level, in considering the extent of the oscillatory motion of the ship due to the natural conditions such as waves and tidal currents.
|
From page 96... ...
o o o o o o o o o o o ~ o ~ U~ o · ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ n ~D 00 0 u~ ~ ~ ~D ~ CD ORE CARRIER FERRYBOAT o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o r 0 oo oo oo oo oo 0 0 oo ~ _ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ U]
|
From page 97... ...
The study plan included a preliminary phase to def ine the design criteria and .to chaise the chancel repute., bS~;£~ d~led~; s`~di~ Are then made for the design of the chosen channel route which included the determination of the channel cross-section profile, various studies of sedimentation, the removal of wrecks and mines, and the study of required nautical equipment. The dredged channel depth criteria were derived in this second phase as follows: Channel Depth Methodology The provisional channel depth was first determined on the basis of a combination of design draft and tidal "windows" for the design vessels.
|
From page 98... ...
Kee 1 Clearance Criteria The channel depth needed in the access route to Zeebrugge was determined as a function of: o The draft of design vessels; o The keel clearance to be observed in the access to Zeebrugge; o The water leve 1 at the time of entering or leaving the harbor , which is a function of the tidal windows for each type of ship. Keel clearances for good and bad weather were calculated separately.
|
From page 99... ...
Draft keel clearance Accuracy of the soundings and tide measurements Divergency from average tide level _ Sedimentation between two surveys and inaccuracies of dredging work \ ~ 1
|
From page 100... ...
, the s underkeel clearance amounts to 12 . 7 percent of ship draft for normal conditions and to 22 percent for bad weather conditions.
|
From page 102... ...
The British Ports Association offered the following summary to the panel: Traffic Underkeel Clearance Port A Almost exclusively VLCCs Port B Port C Port D Port E Port F Port G VLCCs, bulk carriers, general cargo ships VLCCs, containerships, general cargo ships and passenger ships VLCCs, bulk carriers, general cargo ship s VLCCs, bulk carriers, general cargo ships ROW RO f erries and general cargo ships to 4.8 m, or 16 ft. draft Similar to Port F ~ 1096 in excess of draf t f or well -sheltered channe 1 0 .9 m ~ 3 f t ~ f or sheltered waters; 2.3 m {8 ft)
|
From page 103... ...
Another simple technique is essentially similar to the criteria used for designing channel depths: addition of allowances for squat, trim, and other factors to the ship's static draft (Figure 40)
|
From page 104... ...
(SWELL AND SQUAT) ~ _ _ _ _ _ _ _ _ _ _ _ NET UND£RKEtL CLEARANCE SOUNDING ACCURACY SEDI MENTATION BETWEEN DREDGINGS TOLERANCE FOR DREDGING Figure 4 0 Conventional net underkeel clearance calculation, def initions from PIANC TIDAL UNCERTAINTY PREDICTED TIDE 1 CHA.R:IED DEPTFt 1 CHART I'ATU M ~ _ _ _ _ _ _ STATIC DRAFT UNCERTAINTY UNCERTAl~JS=~7 CHARTED DEPTH UNCERTAINTY NOMINAL SEABED ~ SHIP rWATER LINE STATIC DRAFT 4_ _ _,~ _ .
|
From page 105... ...
S rule of thumb in the design of channel depths today would prove cumbersome, as it relies on several estimates f or ship behavior .
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.