Engineering:Under keel clearance
In seafaring, under keel clearance (UKC) is the vertical distance between seabed and the keel or hull of a ship.[1][2][3]
It is used to ensure sufficient navigable water is available for ships at sea.[4][5][1][6]
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.[7][3] Ships typically calculate their UKC to meet criteria for ports to minimise the risk of maritime incidents.[3] The minimum UKC determined includes a safety margin.[7]
Methods of calculation
At a basic level, it is typically calculated in metres using the formula:[1]
- UKC = Charted Depth − Draft -/+ Height of Tide
Ship masters and deck officers can obtain the depth of water from Electronic navigational charts.[5] More dynamic or advanced calculations include safety margins for manoeuvring effects and squat.[7]
Computer systems and software can be used to manage and calculate UKC for ships and ports.[8][9] These include systems that dynamically manage UKC using models, forecasting and calculations.[10]
The International Hydrographic Organization (IHO) sets a Standard for UKC Management for software and systems: S-129 Under Keel Clearance Management.[11]
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.33 C.F.R. 157.450 The regulations require the master to discuss the UKC calculation with the maritime pilot as the ship approaches US ports/waters.33 C.F.R. 157.450
The Australian Maritime Safety Authority state that maintaining adequate UKC is important for safe navigation in the Torres Strait.[12]
Inadequate UKC, caused by shallow water and squat may lead to ship groundings.[13] 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.[13]
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.[14][15]
References
- ↑ 1.0 1.1 1.2 Weintrit, Adam (2009-06-02). Marine Navigation and Safety of Sea Transportation. Boca Raton : London: CRC Press. p. 484. ISBN 978-0-203-86934-5. OCLC 435419166.
- ↑ "Simplified approach to operationalise UKC calculations Conference Paper". PIANC. https://www.researchgate.net/publication/328575846_Simplified_approach_to_operationalise_UKC_calculations.
- ↑ 3.0 3.1 3.2 "All you ever wanted to know about Under Keel Clearance but were afraid to ask". Nautical Institute. https://www.nautinst.org/resources-page/all-you-ever-wanted-to-know-about-under-keel-clearance-but-were-afraid-to-ask.html.
- ↑ Gilardoni, Eduardo O.; Presedo, Juan P. (2017). Navigation in Shallow Waters. Livingston, Scotland: Witherby Publishing Group. p. 67. ISBN 978-1-85609-667-6.
- ↑ 5.0 5.1 ECDIS Safety Settings and UKC Management. Livingston, Scotland: Witherby Publishing Group. 2017. ISBN 9781914993695.
- ↑ "What Is Underwater Keel Clearance?". Marine Insight. https://www.marineinsight.com/naval-architecture/what-is-underwater-keel-clearance/.
- ↑ 7.0 7.1 7.2 ECDIS Passage Planning and Watchkeeping. Livingston, Scotland: Witherby Publishing Group. 2023. p. 25. ISBN 9781856098168.
- ↑ "Under Keel Clearance Technology Wins International Award". Maritime Executive. https://maritime-executive.com/corporate/under-keel-clearance-technology-wins-international-award.
- ↑ "Under Keel Clearance System Upgrade for Bunbury". Daily Cargo News. https://www.thedcn.com.au/news/ports/under-keel-clearance-system-upgrade-for-bunbury/.
- ↑ "OMC". International Harbour Masters Association. https://harbourmaster.org/sponsors/omc.
- ↑ "Dynamic Draft and Under Keel Clearance". International Hydrographic Organization (IHO). https://ihr.iho.int/articles/dynamic-draft-and-under-keel-clearance-a-hydrographic-view/.
- ↑ "Under Keel Clearance Management System Fact Sheet". Australian Maritime Safety Authority. https://www.amsa.gov.au/file/2927/download?token=uVFmyG_S#:~:text=What%20is%20Under%20Keel%20Clearance,ship's%20hull%20and%20the%20seabed..
- ↑ 13.0 13.1 "MAIB: Shallow Water Effects Contributed to Ro/Ro's Grounding". Maritime Executive. https://maritime-executive.com/article/maib-shallow-water-effects-contributed-to-ro-ro-s-grounding.
- ↑ "Panama Canal water levels cause long-term concern". Riviera. https://www.rivieramm.com/news-content-hub/news-content-hub/panama-canal-water-levels-causing-long-term-concern-61025.
- ↑ "Panama Canal Drought Slows Cargo Traffic". The New York Times. https://www.nytimes.com/interactive/2024/01/26/climate/panama-canal-drought-shipping.html.
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