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Groundings due to Ship Squat

Ship Squat has always existed on smaller and slower vessels when underway. These squats have only been a matter of centimetres and thus have been inconsequential.

However, from the mid-1960s to the present day, ship size steadily has grown until we have Supertankers of the order of 400,000 tonnes dwt and above. These Supertankers have almost outgrown the Ports they visit, resulting in small static even-keel underkeel clearances of 1.0 to 1.5 metres. Alongside this development in ship size has been an increase in Service Speed on several ships for example Container Ships, where speeds have gradually increased from 16 knots up to about 25 knots.

Ship design has seen tremendous changes in the 1980s and 1990s. In Oil Tanker design we have the 'Jahre Viking' with a dwt of 564,739t and an LBP of 440m. This is equivalent to the length of 5 football pitches. Later renamed 'Knock Nevis', she was broken up for scrap in Alang, India during early 2010.

In August 2006, the biggest container ship to date, the 'Emma Maersk', came into service. She has a dwt of 156,907 tonnes, a service speed of 25 kts, an LBP of 381 metres, Br Mld of 56 metres and a draft Mld of 14 metres. In March 2007, she became the longest ship in the shipping industry.

As the static underkeel clearances have decreased and as the Service Speeds have increased, ship squats have gradually increased. They can now be of the order of 1.50 to 1.75 metres, which are, of course, by no means inconsequential.

Bryan Barrass now has a database of 113 vessels that have gone aground attributable (wholly or in part) to excessive ship squat.

To help focus the mind on the dangers of excessive squat, one only has to recall the recent groundings of the fourteen vessels listed below:

1. 03/04/10 - Shen Neng 1 - Bulk Carrier - Great Barrier Reef - Australia

2. 10/06/09 - Akti N - Oil Tanker - Vlissinger - The Netherlands

3. 01/02/08 - Riverdance - Ro-Ro vessel - Shell Flat, Blackpool - UK

4. 02/01/08 - LT Cortesia- Container Ship - Varne Bank, Dover - UK

5. 29/12/06 - Emsland - Cargo Ship - Montrose - UK

6. 04/01/06 - Desh Rakshak - Oil Tanker - Port Phillip Bay, Melbourne - Australia

7. 15/12/05 - Kentucky Highway - Ro-Ro vessel - Parana River - Chile

8. 27/07/03 - Eastern Honour 100,000t dwt Tanker - Marsden Pt - New Zealand

9. 31/03/01 - Don Raul Bulk Carrier - Pulluche Canal - Chile

10. 05/02/99 - Napoleon Bonaparte Passenger Liner - Marseilles - France

11. 02/07/97 - Diamond Grace 260,000t dwt VLCC - Tokyo Harbour - Japan

12. 15/02/96 - Sea Empress Supertanker - Milford Haven - UK

13. 07/08/92 - QE2 Passenger Liner - Massachusetts - USA

14. 06/03/87 - Herald of Free Enterprise Ro-Ro vessel - Zeebrugge - Belgium

In the United Kingdom, over the last 40 years the Department for Transport (DfT). have shown their concern by issuing eight 'M' notices concerning the problems of ship squat and accompanying problems in shallow water. These alert all Mariners to the associated dangers.

It is important for shipboard officers to recognise the signs when a ship has entered shallow water conditions