Year: 1998 Language: english Author: Bruce B. Parker and Lloyd C. Huff Format: PDF Quality: eBook Pages count: 23 Description: The determination of under-keel clearance (UKC) became a critical factor in safe and efficient navigation when modern vessels became so large that they could not enter major ports except near times of high water. Because inaccurate determination of UKC can have serious safety and/or economic consequences, many ports provide guidelines for minimum under-keel clearance in their navigation channels. These guidelines essentially provide a safety margin that reflects their best judgment on present capabilities to determine UKC in these waterways. They can be based on such things as how recently charted depths have been updated by surveys, or how much the wind might cause the water level to be lower than the predicted tide. If such guidelines specify a minimum UKC that is too large, then the result may be economic losses due to less cargo being carried, unnecessary lightering, or unnecessary delay while waiting outside the entrance for higher water. If such guidelines allow a minimum UKC that is too small, then groundings may occur, which could have economic consequences if the grounding closes the port or leads to property damage, as well as environmental consequences if a hazardous spill results. (When a ship has too little UKC it loses maneuverability, so a collision is also possible.)
Contents
This paper provides an overview of recent technological developments that have improved the ability to manage under-keel clearance (UKC) in ports. The inaccurate determination of the UKC of large-draft ships entering or leaving depthlimited ports can have serious safety, economic, and environmental consequences. A ship's master can manage his ship's UKC by: (1 ) taking actions that affect the ship's dynamic draft (such as changing the ship's speed) and (2) scheduling his ship's transit of the planned route to ensure that there will be sufficient water level for safe passage when the ship reaches locations with controlling depths. To do this, however, he must have accurate real-time and forecast environmental information along his route, as well as a validated method of predicting his ship's motion (and thus dynamic draft) for various situations. At a minimum, this information must include accurate charted depths and underwater hazards, water levels, and ship-specific channel-specific prediction formulas for dynamic draft (based on ship speed, static draft, and water depth). The dynamic draft calculation may also require information on currents, water density, and waves, swell, and/or seiching. Recently developed systems that can provide the necessary information for UKC management include: nowcast/forecast oceanographic model systems (a necessary step beyond real-time oceanographic systems); on-the-fly GPS systems to provide accurate ship motion data for calibrating dynamic-draft prediction systems; modern hydrographic measurement systems (such as shallowwater multibeam and side-scan sonar systems); and modern electronic nautical chart systems (and their supporting rapid update services). This paper includes discussion of what further improvements to these systems are needed to make effective UKC management a reality.
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Modern Under Keel Clearance Management
Language: english
Author: Bruce B. Parker and Lloyd C. Huff
Format: PDF
Quality: eBook
Pages count: 23
Description: The determination of under-keel clearance (UKC) became a critical factor in
safe and efficient navigation when modern vessels became so large that they could not
enter major ports except near times of high water. Because inaccurate determination
of UKC can have serious safety and/or economic consequences, many ports provide
guidelines for minimum under-keel clearance in their navigation channels. These
guidelines essentially provide a safety margin that reflects their best judgment on
present capabilities to determine UKC in these waterways. They can be based on such
things as how recently charted depths have been updated by surveys, or how much the
wind might cause the water level to be lower than the predicted tide. If such guidelines
specify a minimum UKC that is too large, then the result may be economic losses due
to less cargo being carried, unnecessary lightering, or unnecessary delay while waiting
outside the entrance for higher water. If such guidelines allow a minimum UKC that is
too small, then groundings may occur, which could have economic consequences if the
grounding closes the port or leads to property damage, as well as environmental
consequences if a hazardous spill results. (When a ship has too little UKC it loses
maneuverability, so a collision is also possible.)
Contents
This paper provides an overview of recent technological developments thathave improved the ability to manage under-keel clearance (UKC) in ports. The
inaccurate determination of the UKC of large-draft ships entering or leaving depthlimited
ports can have serious safety, economic, and environmental consequences.
A ship's master can manage his ship's UKC by: (1 ) taking actions that affect the ship's
dynamic draft (such as changing the ship's speed) and (2) scheduling his ship's transit
of the planned route to ensure that there will be sufficient water level for safe passage
when the ship reaches locations with controlling depths. To do this, however, he must
have accurate real-time and forecast environmental information along his route, as well
as a validated method of predicting his ship's motion (and thus dynamic draft) for
various situations. At a minimum, this information must include accurate charted depths
and underwater hazards, water levels, and ship-specific channel-specific prediction
formulas for dynamic draft (based on ship speed, static draft, and water depth). The
dynamic draft calculation may also require information on currents, water density, and
waves, swell, and/or seiching. Recently developed systems that can provide the
necessary information for UKC management include: nowcast/forecast oceanographic
model systems (a necessary step beyond real-time oceanographic systems); on-the-fly
GPS systems to provide accurate ship motion data for calibrating dynamic-draft
prediction systems; modern hydrographic measurement systems (such as shallowwater
multibeam and side-scan sonar systems); and modern electronic nautical chart
systems (and their supporting rapid update services). This paper includes discussion
of what further improvements to these systems are needed to make effective UKC
management a reality.
Screenshots
MODERN UNDER-KEEL CLEARANCE MANAGEMENT DYNAMIC DRAFT.pdf
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