Under keel clearance
{{Short description|Height of water under a keel}}
In seafaring, under keel clearance (UKC) is the vertical distance between seabed and the keel or hull of a ship.{{Cite web |url=https://www.researchgate.net/publication/328575846_Simplified_approach_to_operationalise_UKC_calculations |title=Simplified approach to operationalise UKC calculations Conference Paper |access-date=4 April 2024 |publisher=PIANC}}{{Cite web |url=https://www.nautinst.org/resources-page/all-you-ever-wanted-to-know-about-under-keel-clearance-but-were-afraid-to-ask.html |title=All you ever wanted to know about Under Keel Clearance but were afraid to ask |access-date=4 April 2024 |publisher=Nautical Institute}}
It is used to ensure sufficient navigable water is available for ships at sea.{{cite book | last=Gilardoni | first=Eduardo O. | last2=Presedo | first2=Juan P. | title=Navigation in Shallow Waters | publisher=Witherby Publishing Group | publication-place=Livingston, Scotland | date=2017 | isbn=978-1-85609-667-6|page=67}}{{cite book | title=ECDIS Safety Settings and UKC Management | publisher=Witherby Publishing Group | publication-place=Livingston, Scotland | date=2017 | isbn=9781914993695}}{{cite book | last=Weintrit | first=Adam | title=Marine Navigation and Safety of Sea Transportation | publisher=CRC Press | publication-place=Boca Raton : London | date=2009-06-02 | isbn=978-0-203-86934-5 | oclc=435419166 | page=484}}{{Cite web |url=https://www.marineinsight.com/naval-architecture/what-is-underwater-keel-clearance/|title=What Is Underwater Keel Clearance? |access-date=4 April 2024 |publisher=Marine Insight}}
Master mariners should ensure there is sufficient minimum UKC for their ships; ports should ensure sufficient minimum UKC for the type and draft of ships due to arrive in the port.{{cite book | title=ECDIS Passage Planning and Watchkeeping | publisher=Witherby Publishing Group | publication-place=Livingston, Scotland | date=2023 | isbn=9781856098168|page=25}} Ships typically calculate their UKC to meet criteria for ports to minimise the risk of maritime incidents. The minimum UKC determined includes a safety margin.
Methods of calculation
At a basic level, it is typically calculated in metres using the formula:
:UKC = Charted Depth − Draft -/+ Height of Tide
Ship masters and deck officers can obtain the depth of water from Electronic navigational charts. More dynamic or advanced calculations include safety margins for manoeuvring effects and squat.
Computer systems and software can be used to manage and calculate UKC for ships and ports.{{Cite web|url=https://maritime-executive.com/corporate/under-keel-clearance-technology-wins-international-award |title=Under Keel Clearance Technology Wins International Award |access-date=4 April 2024 |publisher=Maritime Executive}}{{Cite web|url=https://www.thedcn.com.au/news/ports/under-keel-clearance-system-upgrade-for-bunbury/ |title=Under Keel Clearance System Upgrade for Bunbury |access-date=4 April 2024 |publisher=Daily Cargo News}} These include systems that dynamically manage UKC using models, forecasting and calculations.{{Cite web|url=https://harbourmaster.org/sponsors/omc |title=OMC |access-date=4 April 2024 |publisher=International Harbour Masters Association}}
The International Hydrographic Organization (IHO) sets a Standard for UKC Management for software and systems: S-129 Under Keel Clearance Management.{{Cite web |url=https://ihr.iho.int/articles/dynamic-draft-and-under-keel-clearance-a-hydrographic-view/ |title=Dynamic Draft and Under Keel Clearance |access-date=4 April 2024 |publisher=International Hydrographic Organization (IHO)}}
Uses and requirements
For US waters, the US Code of Federal Regulations require ships and their masters to calculate UKC based on the ship's deepest navigational draft.{{CodeFedReg |33|157|450}} The regulations require the master to discuss the UKC calculation with the maritime pilot as the ship approaches US ports/waters.{{CodeFedReg |33|157|450}}
The Australian Maritime Safety Authority state that maintaining adequate UKC is important for safe navigation in the Torres Strait.{{Cite web |url=https://www.amsa.gov.au/file/2927/download?token=uVFmyG_S#:~:text=What%20is%20Under%20Keel%20Clearance,ship's%20hull%20and%20the%20seabed. |title=Under Keel Clearance Management System Fact Sheet |access-date=4 April 2024 |publisher=Australian Maritime Safety Authority}}
Inadequate UKC, caused by shallow water and squat may lead to ship groundings.{{Cite web|url=https://maritime-executive.com/article/maib-shallow-water-effects-contributed-to-ro-ro-s-grounding |title=MAIB: Shallow Water Effects Contributed to Ro/Ro's Grounding |access-date=4 April 2024 |publisher=Maritime Executive}} In 2019, the UK Marine Accident Investigation Branch found that indequate UKC contributed towards the grounding of the ro/ro freight ferry MS Stena Performer.
Changes in water level may cause issues with adequate UKC for ships. For example, recent water level reductions in the Panama Canal have reduced UKC for ships meaning some ships are not able to transit the canal.{{Cite web|url=https://www.rivieramm.com/news-content-hub/news-content-hub/panama-canal-water-levels-causing-long-term-concern-61025 |title=Panama Canal water levels cause long-term concern |access-date=4 April 2024 |publisher=Riviera}}{{Cite web|url=https://www.nytimes.com/interactive/2024/01/26/climate/panama-canal-drought-shipping.html |title=Panama Canal Drought Slows Cargo Traffic |access-date=4 April 2024 |publisher=The New York Times}}
References
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{{Ship measurements}}