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'Once in a millennium' rogue wave recorded off Ucluelet

The 17.6-metre swell was almost three times as tall as the waves around it, researchers say.

A giant wave off Ucluelet on Nov. 17, 2020 is the most extreme rogue wave ever recorded, says a group of Victoria scientists.

The 17.6-metre swell — as high as a four-storey building — was recorded with sensor buoys at Amphitrite Bank, about seven kilometres off Ucluelet, during one of the heaviest storms of the year. No ships were in the area at the time.

Recorded by Victoria-based MarineLabs Data Systems, it’s the subject of a recently published article in the journal ­Scientific Reports by Johannes Gemmrich and Leah Cicon, both of the University of Victoria.

Rogue waves, also known as freak or killer waves, are defined as waves with a height more than double that of the waves around them. They occur unexpectedly with a huge force that makes them ­especially dangerous for marine vessels.

The first rogue wave ever measured was off the coast of Norway in 1995. The “Draupner Wave” measured 25.6 metres in a sea state with wave heights of about 12 metres, meaning it was more than twice the height of those around it.

The wave recorded by MarineLabs off Ucluelet was 17.6 metres in a sea state with wave heights of six metres, so it was nearly three times the size of the waves around it.

“Proportionally, the Ucluelet wave is likely the most extreme rogue wave ever recorded,” said Gemmrich, who studies large wave events along B.C.’s coast as part of his work as a research physicist at the University of Victoria. “Only a few rogue waves in high sea states have been observed directly, and nothing of this magnitude.”

Gemmrich said such a wave would probably occur once in 1,300 years.

The sensor buoy is part of MarineLabs’ CoastAware network, which provides data from 26 sensor buoys placed on ­coastlines and in oceans around North America.

This year, the company plans to more than double its number of sensor locations, bringing its fleet of buoys to close to 70 by year-end.

MarineLabs CEO Scott Beatty said the unpredictability of rogue waves, and the sheer power of the “walls of water,” can make them incredibly dangerous to marine vessels and the public.

“The potential of ­predicting rogue waves remains an open question, but our data is ­helping to better understand when, where and how rogue waves form, and the risks that they pose,” he said.

“Capturing this once-in-a-­millennium wave, right in our backyard, is a thrilling indicator of the power of coastal intelligence to transform marine safety.”

Beatty said the waves have the ability to cause “wave run-up” on shorelines, putting people on the beach at risk of being swept out to sea.

Cicon, co-author of the report, is a master’s student at the University of Victoria whose research includes analysis of rogue waves, and ­implementation of a wave model for routinely forecasting the rogue-wave risk on B.C.’s coast. She also works part time for Environment and Climate Change Canada on wave models for wave climate applications.

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