Under keel clearance

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Under keel clearance (UKC) is the term and calculations used in seafaring to ensure sufficient navigable water is available for ships at sea. [1] [2] [3] [4] It is most commonly described as the height and width of available water below the keel (hull of a ship). [3] [5] More simply, it can be described as how much water is left between the bottom of the ship and the seabed. [6]

Contents

Master mariners should ensure there is sufficient minimum UKC for their ships and ports should ensure sufficient minimum UKC for the type and draft of ships due to arrive in the port. [7] [6] Ships typically calculate their UKC to meet criteria for ports to minimise the risk of maritime incidents. [6] A minimum UKC value is determined, which includes a safety margin. [7]

Methods of calculation

At a basic level, it is typically calculated in metres using the formula: Charted Depth − Draft -/+ Height of Tide = UKC. [3] Ship masters and deck officers can obtain the depth of water from Electronic navigational charts. [2] 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 CFR 157.450 The regulations require the master to discuss the UKC calculation with the maritime pilot as the ship approaches US ports/waters. 33 CFR 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]

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<span class="mw-page-title-main">International Maritime Organization</span> Specialised agency of the United Nations

The International Maritime Organization is a specialised agency of the United Nations responsible for regulating maritime transport. The IMO was established following agreement at a UN conference held in Geneva in 1948 and the IMO came into existence ten years later, meeting for the first time on 17 March 1958. Headquartered in London, United Kingdom, the IMO currently has 176 Member States and three Associate Members.

<span class="mw-page-title-main">Navigation</span> Process of monitoring and controlling the movement of a craft or vehicle from one place to another

Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another. The field of navigation includes four general categories: land navigation, marine navigation, aeronautic navigation, and space navigation.

<span class="mw-page-title-main">Seamanship</span> Art, knowledge and competence of operating a craft on water

Seamanship is the art, knowledge and competence of operating a ship, boat or other craft on water. The Oxford Dictionary states that seamanship is "The skill, techniques, or practice of handling a ship or boat at sea."

<span class="mw-page-title-main">Hydrographic survey</span> Science of measurement and description of features which affect maritime activities

Hydrographic survey is the science of measurement and description of features which affect maritime navigation, marine construction, dredging, offshore wind farms, offshore oil exploration and drilling and related activities. Surveys may also be conducted to determine the route of subsea cables such as telecommunications cables, cables associated with wind farms, and HVDC power cables. Strong emphasis is placed on soundings, shorelines, tides, currents, seabed and submerged obstructions that relate to the previously mentioned activities. The term hydrography is used synonymously to describe maritime cartography, which in the final stages of the hydrographic process uses the raw data collected through hydrographic survey into information usable by the end user.

Tonnage is a measure of the cargo-carrying capacity of a ship, and is commonly used to assess fees on commercial shipping. The term derives from the taxation paid on tuns or casks of wine. In modern maritime usage, "tonnage" specifically refers to a calculation of the volume or cargo volume of a ship. Although tonnage (volume) should not be confused with displacement, the long ton of 2,240 lb is derived from the fact that a "tun" of wine typically weighed that much.

Panamax Largest ships that can transit the Panama Canal

Panamax and New Panamax are terms for the size limits for ships travelling through the Panama Canal. The limits and requirements are published by the Panama Canal Authority (ACP) in a publication titled "Vessel Requirements". These requirements also describe topics like exceptional dry seasonal limits, propulsion, communications, and detailed ship design.

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<span class="mw-page-title-main">Electronic navigational chart</span> Digital Map

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<span class="mw-page-title-main">Maritime pilot</span> Mariner who maneuvers ships through dangerous or congested waters

A maritime pilot, marine pilot, harbor pilot, port pilot, ship pilot, or simply pilot, is a mariner who has specific knowledge of an often dangerous or congested waterway, such as harbors or river mouths. Maritime pilots know local details such as depth, currents, and hazards. They board and temporarily join the crew to safely guide the ship's passage, so they must also have expertise in handling ships of all types and sizes. Obtaining the title "maritime pilot" requires being licensed or authorised by a recognised pilotage authority.

<span class="mw-page-title-main">Draft (hull)</span> Depth of a vessel below its waterline

The draft or draught of a ship is a determined depth of the vessel below the waterline, measured vertically to its hull's lowest—its propellers, or keel, or other reference point. Draft varies according to the loaded condition of the ship. A deeper draft means the ship will have greater vertical depth below the waterline. Draft is used in under keel clearance calculations, where the draft is calculated with the available dept of water to ensure the ship can navigate safely, without grounding.

<span class="mw-page-title-main">Air draft</span> Distance from water to the highest point on a vessel or lowest point on a bridge span

Air draft is the distance from the surface of the water to the highest point on a vessel. This is similar to the deep draft of a vessel which is measured from the surface of the water to the deepest part of the hull below the surface. However, air draft is expressed as a height, while deep draft is expressed as a depth.

<span class="mw-page-title-main">Passage planning</span>

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<span class="mw-page-title-main">Ship stability</span> Ship response to disturbance from an upright condition

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<span class="mw-page-title-main">Squat effect</span> Effect of reduced pressure under a hull making way, causing a downward displacement

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References

  1. ↑ Gilardoni, Eduardo O.; Presedo, Juan P. (2017). Navigation in Shallow Waters. Livingston, Scotland: Witherby Publishing Group. p. 67. ISBN   978-1-85609-667-6.
  2. 1 2 ECDIS Safety Settings and UKC Management. Livingston, Scotland: Witherby Publishing Group. 2017. ISBN   9781914993695.
  3. 1 2 3 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.
  4. ↑ "What Is Underwater Keel Clearance?". Marine Insight. Retrieved 4 April 2024.
  5. ↑ "Simplified approach to operationalise UKC calculations Conference Paper". PIANC. Retrieved 4 April 2024.
  6. 1 2 3 "All you ever wanted to know about Under Keel Clearance but were afraid to ask". Nautical Institute. Retrieved 4 April 2024.
  7. 1 2 3 ECDIS Passage Planning and Watchkeeping. Livingston, Scotland: Witherby Publishing Group. 2023. p. 25. ISBN   9781856098168.
  8. ↑ "Under Keel Clearance Technology Wins International Award". Maritime Executive. Retrieved 4 April 2024.
  9. ↑ "Under Keel Clearance System Upgrade for Bunbury". Daily Cargo News. Retrieved 4 April 2024.
  10. ↑ "OMC". International Harbour Masters Association. Retrieved 4 April 2024.
  11. ↑ "Dynamic Draft and Under Keel Clearance". International Hydrographic Organization (IHO). Retrieved 4 April 2024.
  12. ↑ "Under Keel Clearance Management System Fact Sheet". Australian Maritime Safety Authority. Retrieved 4 April 2024.
  13. 1 2 "MAIB: Shallow Water Effects Contributed to Ro/Ro's Grounding". Maritime Executive. Retrieved 4 April 2024.
  14. ↑ "Panama Canal water levels cause long-term concern". Riviera. Retrieved 4 April 2024.
  15. ↑ "Panama Canal Drought Slows Cargo Traffic". The New York Times. Retrieved 4 April 2024.
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