Rogue waves and the case for routeing ships around storms
The increasing severity and frequency of storms – and so-called rogue waves – pose a serious threat to shipping.
The threat stemming from rogue waves, capable of exerting forces of approximately 100 tonnes per square metre, is far greater than the 15 tonnes/m2 that ships are usually designed to withstand.
Moreover, due to their short-lived nature and the fact that global coverage of the oceans by satellite-based sensors is not continuous, it is impracticable for marine authorities to issue early warnings of their existence.
For years, such waves were thought to be very rare events (one every 10,000 years) and the numerous reported sightings were dismissed as gross exaggerations.
However, in 1995, a wave recorder mounted on the Draupner oil rig in the North Sea recorded a wave that was 25.6 metres in height (trough to crest). Additional evidence comes from examination of the wreckage of MS München, which sank during a North Atlantic storm in 1978, coupled with the testimonies of highly experienced seafarers – the Masters of MS Queen Elizabeth II (damaged by a rogue wave in the North Atlantic during 1995), MS Bremen and MS Caledonian Star (both damaged by rogue waves in the South Atlantic during 2001).
Since 1995, these waves have been the subject of intense scientific study, for example, the EU-sponsored MAXWAVE project (2000-2003), and there is clear evidence that such waves occur much more frequently (10 detected in the North Atlantic by satellite-based sensors during a three-week period in 2001).
In the heavy seas associated with high winds and storm conditions, there is a significant risk of parametric rolling, especially for large box ships with flared bows. In addition, ships’ hulls are routinely subjected to huge stresses and strains during storm conditions due to a combination of panting, racking, slamming and hogging & sagging.
Minimising the risk to shipping
In light of the accepted method of determining risk (consequence x probability), it is submitted there is now a significant risk of a ship being damaged (or worse) in storm conditions.
Moreover, since there is a requirement to keep risk as low as reasonably practicable (ALARP), it is suggested there are only two possible ways of achieving this:
Option 1: make ships much stronger.
Option 2: route ships around major storms.
Since the first option is costly and therefore likely resisted by both the shipping industry and governments, the most viable solution is the second.
Routeing ships around major storms will not only save lives and reduce injuries but also significantly reduce the number of ships foundering in bad weather. In addition, the impact of foundering ships on the marine environment and associated industries can often be catastrophic as exemplified by the Erika and Prestige oil spills.
Alas, safety concerns frequently play second fiddle to economic interests. Yet, the economic case for routeing ships around major storms is very strong.
Of particular concern is the number of containers lost at sea each year in adverse weather conditions with the loss of approximately 1,816 containers from the vessel ONE Apus in 2020 and nearly 300 containers from the MSC Zoe in 2019 being classic cases in point.
While reported annual losses average 1,390 (research conducted by the World Shipping Council), many losses are either not noticed or never reported and it is estimated that annual losses could well exceed 10,000. Since a significant number of these containers (64 in the case of ONE Apus) contain dangerous goods, there are serious ramifications for the marine environment.
The argument against ship routeing has always been the need for additional time and fuel to complete the journey. However, research has shown that the shortest route is not always the quickest route and that taking advantage of calmer seas, coupled with careful management of ship trim, can reduce fuel consumption by as much as 5%.
In addition, there is the potential for reduced insurance premiums due to the reduction in damage and loss-related claims.
In view of the significant threat to ships, their crews and the marine environment posed by rogue waves and parametric rolling in storm conditions coupled with the economic arguments, it seems clear there is a strong case for routeing ships around major storms.
The views expressed in this article are those of the author and do not reflect the official stance of the Institute.
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Image: container ship in stormy seas; credit: Shutterstock.
