Under keel clearance management

Using an advanced under keel clearance management (UKCM) system will reduce your chances of running aground.

Maintaining a safe vertical distance between your ships hull and the ocean floor keeps the keel clear of the seabed and reduces the chances of running aground.

What is a UKCM system?

The under keel clearance management (UKCM) system helps large ships to navigate through the Torres Strait in Australia's north.

The system implemented by AMSA, for use by coastal pilots when transiting ships with a draught greater than nine metres through Torres Strait, calculates the depth of water underneath the keel throughout the transit in near real-time, taking account of a number of variables, including the height of tide, the speed of the ship, the ship’s squat, tidal streams and the dynamic motions of the vessel.

The UKCM system receives input from a number of sensors deployed at various locations through the system’s area of operations, as well as data from the ship via the ship’s onboard Automatic Identification System (AIS).

UKCM for ships transiting Torres Strait

AMSA operates a UKCM system in Torres Strait that helps large ships to safely navigate through the Torres Strait, in Australia's north.

The UKCM system put in place by AMSA, is primarily for use by coastal pilots when transiting ships through a specific section of Torres Strait. The system calculates in near real time, the depth of water underneath the keel throughout the transit, taking account of:

the height of tide
tidal streams
the speed of the ship
dynamic motions of the ship (ie squat and heel).

AMSA regulation of under keel clearance in Torres Strait

Details of under keel clearance requirements in Torres Strait are provided in Marine Order 54 (Coastal pilotage).

Marine Order 54 outlines that pilots of ships transiting Torres Strait with draughts of 8 metres up to 12.2 metres must have a UKCM system plan.

On 1 November 2021, changes were made to Marine Order 54, with the issue of Marine Order 54 (Torres Strait draught variation) – Exemption 2021.

The changes mean that pilots of ships transiting Torres Strait with draughts of 9 metres up to 12.5 metres must have a UKCM system plan.

The changes to minimum and maximum draught limits came about following extensive sea trials. A comprehensive analysis report confirmed the accuracy of the Torres Strait UKCM system for ships up to 12.5 metres draught.

While the maximum permitted draught of vessels transiting Torres Strait has increased, the amount of under keel clearance required has not changed.

UKCM system background information

The original Marine Order 54 draught limitation of 12.2 metres reflected the previous imperial measure of 40 feet, which was based on a study conducted in the 1970’s by the (then) Federal Department for Transport.

Vessels with a draught of 12.2 metres were thought to be able to pass through Torres Strait on any day of the year while maintaining the required under keel clearance. Ships were restricted to conducting the transit during projected periods of high water.

Following the introduction of compulsory pilotage in Torres Strait in 2006, another study investigated whether a new method could provide better safety margins and economic benefits for ships.

The 2007 study report recommended a UKCM system for ships with draughts between 8 metres and 12.2 metres.

We declared the UKCM system ‘operational’ in December 2011.

Use of the UKCM system (by AMSA-licensed coastal pilots assigned to the transit of ships through Varzin Passage, Gannet Passage and the Prince of Wales Channel) became a condition of pilotage providers’ licences in January 2014.

The requirement to use the UKCM system was included in Marine Order 54 (Coastal pilotage) in July 2014.