Research suggests that ‘freak’ waves of up to 30m high are causing disasters at sea. But the maritime industry faces claims that it is avoiding the re-engineering needed to cope. Richard Fisher reports
In 1995 off the coast of
Luckily the QE2 escaped relatively unscathed, but others have not been so fortunate. Only last week the tourist ship Voyager limped back to port with eight injured passengers and no communications after a heavy battering in stormy Mediterranean seas. In the midst of the storm, reports described a single wave so big it smashed the bridge windows.
As the world ponders the lessons of the Asian tsunami, some experts believe rogue or ‘freak’ waves — though different in nature and origin — pose a real threat to shipping that is being ignored.
A growing number of researchers and naval architects claim that many of the ships lost to ‘bad weather’ may well have been hit by a single monster wave. Some claim that one of these waves was to blame for the infamous sinking of the Derbyshire bulk carrier, a brand-new ship, off
Calls to engineer ships to cope with rogue waves have gone unheard, however. The standard linear wave models of the ocean ignore these anomalies, classing them as so rare that ships need not be engineered to survive them. The classification societies that set design standards for ships have stalled on action to improve standards, and the nations that regulate them have failed to step in.
The offshore industry, in contrast, has responded by building stronger platforms against abnormal conditions after a series of losses including the Ocean Ranger disaster in
There have been no major rig incidents involving rogue waves since, but disturbingly for mariners and ship passengers a raft of recent research has shown that these waves are much more frequent than previously thought. A series of conferences in the past few years have focused on them, including the Royal Institution of Naval Architects’ Design and Operation for Abnormal Conditions event last month. The consensus among academics and ship designers there was that terms like ‘freak’ or ‘monster’ waves implied that these waves were so rare that nothing could be done. Indeed, conventional knowledge suggests that sea states of the rogue wave size should only occur around every 10,000 years, but this is clearly not the case as technology reveals fresh evidence of their frightening regularity.
Leading the research has been the EU-funded Maxwave project, which used ESA satellite radar data to map the sea for three weeks. The team spotted more than 10 waves over 25m high. A follow-on project, WaveAtlas, starting in the next few months will analyse two years’ data, and if funding problems can be overcome, the researchers processing the images at the German Aerospace Centre hope to reveal their results later this year.
Prof Wolfgang Rosenthal, Maxwave project leader and one of the WaveAtlas co-ordinators from GKSS coastal research institute in Germany, said previous methods of measuring rogue waves relied on eyewitness testimony and the chance that disparate oceanographic buoys might catch one.
‘With these imagettes we’ll get wave data every 7km along the satellite orbit to compare with the storm hindcasts,’ he said. ‘It’s an exciting time because we’ll have statistics from the full globe. I think we’ll find higher waves that are made in a different way than previously thought.’ The eventual aim is to release all the data collected from the satellites since they were launched in 1990, according to ESA’s European Remote Sensing satellite mission manager.
However, research like this has not convinced the shipping industry that design changes need to be made, said Rosenthal. ‘The classification societies are very old fashioned. Waiting for definitive proof is sometimes an excuse,’ he said. ‘Our results so far are clear. I cannot accept this attitude that “more research should be done before we act”. What else can we do if we show these people the measurements and they still say that these waves do not exist?’
Allan Graveson, senior national secretary of mariner’s union NUMAST, points to an ‘incestuous’ relationship between classification society, shipbuilder and owner that has led to a sluggish response to any calls for safety improvements. He explained that the responsibility for setting standards, once the preserve of the state, has been handed down to classification societies. ‘This means competitive forces come into play over safety. The classification societies don’t want to lose business to each other. The owner is looking for the cheapest deal he can get.’
The International Association of Classification Societies (IACS), including
There are three areas in need of urgent re-engineering for abnormal seas, according to rogue wave researchers: hull girder strength against bending is inadequate; many localised areas such as the hatch cover that failed on the Derbyshire are too weak to withstand massive water ingress; and ship capsize rules are too low for loss of stability due to rolling in head seas. Improvements need not be expensive if put in at the design stage, the researchers claim.
Gil-Yong Han, IACS senior technical officer, said classification design procedures are based on the most recently available data, however. He pointed to the development of a range of new tougher ‘goal-based’ standards for the industry. ‘IACS considers that the information available on freak waves at this stage is not sufficient for IACS members to consider changing their design rules.’
Helge Rathje, head of the hydromechanics service group at IACS member Germanischer Lloyd, is taking a different approach to abnormal conditions. His company is developing a Shipboard Routing Assistance system that uses Met Office data to calculate likely ship damage in dangerous seaways ahead, allowing a new course to be plotted. Rathje rejects the view that classification society competition forces down standards. ‘We are confounded by that argument. Our classification society has values: to safeguard the ship, environment and the crew,’ he said. ‘There’s always been a strong competition between the classes but this has been for the benefit of ship safety. Lowering the standards too much would result in heavy commercial failures.’
Rogue wave researchers hoping to be heard do have another route, however. If they can convince a nation like the
Tom Allan, chair of the Maritime Safety Committee at the IMO, said rogue waves have never been officially discussed and he’d like to see the issue brought before his committee. ‘Bringing it to the Maritime Safety Committee is the next stage of the debate,’ he said. ‘Whether the academics have got it right or wrong they can’t take it further forward until they have the debate with the industry and classification societies. The IMO would be the appropriate body in which to have the debate to pull all that together. The ball is in their court.’
Unfortunately for the rogue wave researchers one of the most respected lobbyists on the subject over the past few years is severely ill, and so the movement has lost one of its loudest and most persuasive voices. Emeritus Prof Douglas Faulkner, ex-chairman of naval architecture at
In the absence of action from classification societies and the
So for the moment worried researchers, ship designers and engineers can only wait and see whether the results of projects like WaveAtlas will convince classification societies or government. Disturbingly NUMAST’s Graveson believes that only a major disaster will bring the issue to wider attention and force action. ‘In the event of a significant loss of life or a major pollution incident, the media and the public would not accept the excuse that “it was the wrong type of wave”.’
Sidebar: Why Do rogue waves form?
Unlike the Asian tsunami, rogue waves are not triggered by earthquakes or landslides, and have nowhere near the same level of devastation. The danger comes for ships or offshore platforms that are unlucky enough to be in the path of a larger and steeper-than-average wave than they are engineered for.
Conventional wave theory states that when the crests of waves travelling at different speeds match in phase they form a larger wave, but this ‘linear modelling’ is insufficient to explain waves of heights around 30m. It is the cause in certain areas such as off
Researchers are looking to non-linear interaction — or chaos — to explain the apparent anomaly of the rogue. Some mathematicians believe tiny changes of conditions on a small scale could produce unexpected consequences, and massive waves. Calculations like the non-linear Schrödinger equation may hold the key, but there has been no eureka moment so far.
William Buckley, one of the leading researchers in the rogue wave field, believes that the waves can be divided into two classes. Type 2 waves form when severe convective winds act on a storm-driven seaway, he said. The transience and rapid dispersion of these waves means that their energy can be relatively low and a ship is very unlucky to meet one.
Type 1 waves, however, are more mysterious and particularly nasty. Buckley describes a non-dispersive wave or wall of water unlike normal storm waves travelling great distances over the ocean, and therefore much more likely to encounter a ship. ‘It will appear in the distance and the crew will see it coming,’ he said. ‘We don’t know how these waves form yet.’