Extreme waves measured off the Isle of Lewis

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WAVES of over 15 metres – the height of a four-storey building and twice the size of normal storm waters – were measured near the north west coast of the Isle of Lewis during the gales on Monday (October 3).

Three recently-installed wave rider buoys made it possible for the first time ever to measure waves in the area. They are part of the Hebridean Marine Energy Futures project at Lews Castle College UHI, part of the University of the Highlands and Islands, which is developing skills, models, data and strategies to inform the nation’s marine energy industry.

Project leader Arne Vogler explained: “The occurrence of 15metre waves - the height of a four-storey building - after half-a-day of severe gale force winds indicates that much higher waves are likely to occur during prolonged storm periods which are often encountered in the area between autumn and spring.”

During the gale which crossed the Outer Hebrides on Monday afternoon, with peak gusts of 66mph, the buoys revealed that extreme waves of over 15metres were up to twice the height of the average waves. The huge rollers were just five nautical miles off north west Lewis.  

Arne Vogler continued: “The ability to measure these kind of events will allow us to gather invaluable baseline data which can be used to assess impacts of climate change and changes of seabed use.”   The buoys, installed at the end of September, are the first stage in a wave data observatory network and transmit live data through a radio link to the shore station.

Mr Vogler added: “We plan to supplement the buoys with seabed mounted profilers closer to shore to enhance the understanding of the wave shoaling processes in the area. 

“This is significant not only to coastal protection, but also to the selection and development of wave energy sites in an area that offers huge potential for energy extraction from the marine environment.

“The ability to measure wave heights at three different locations off Lewis will allow us to evaluate the optimum sites for wave energy developments, and help to develop an understanding of threats and opportunities at our coast by assessing the impact of the highest waves on coastal structures and offshore installations such as wave energy converters. 

“The data will also be of benefit to other sea users such as coastguards, fishermen, fish farm operations and marine support services.”