Tsunami poles project to mark villages’ six-metre safety zone

Haida Gwaii is testing a new way to mark tsunami safe zones — painted telephone and power poles.

An example of the tsunami safety zone markings that will go up on power and telephone poles in villages on Haida Gwaii. Other graphics will be used to warn people they are below the safe zone.

Haida Gwaii is testing a new way to mark tsunami safe zones painted telephone and power poles.

This spring, each village will get a map showing what poles to paint so everyone can quickly see if they are above or below the tsunami warning zone.

On Haida Gwaii, emergency planners have set that zone at six metres above the highest high tide.

“All of the communities on island have signed up,” says Lori Wiedeman, chief administrative officer for the Village of Queen Charlotte. Co-funded by the B.C. government, BC Hydro and Telus, the $25,000 pilot project is the first of its kind.

“We’re a really good place for a pilot project, because each community has a really different geography,” said Wiedeman.

Carmin Moore, a graduate student studying disaster and emergency management at Royal Roads University, is working on Haida Gwaii from November to February to map the poles and test-paint a few markings.

Moore is using LIDAR maps high-resolution laser scans of the Haida Gwaii landscape to trace the six-metre safety zone along all the islands’ populated coastal areas.

After comparing LIDAR maps with local road networks and topography, Moore will recommend which of the over 2,000 utility poles on Haida Gwaii should get the special markings.

The idea was sparked by Larry Duke, the Queen Charlotte fire chief and a member of the all-islands emergency planning group.

Duke said they wanted to use existing infrastructure rather than brand-new signs, so utility poles were a natural choice.

“We really couldn’t find projects like this going on elsewhere, at least not in British Columbia,” said Duke.

Some coastal cities in Thailand have tsunami pole markings, he said, but they show historical wave heights rather than a safety zone.

With the open Pacific and the active Queen Charlotte fault just off the west coast, plus a history of tsunami-generating earthquakes in Prince William Sound and southwest of Vancouver Island, Haida Gwaii has a history of tsunami waves.

That history received a surprise chapter in October 2012, when a 7.8-magnitude thrust quake struck off the west coast of Moresby Island.

“Nobody expected that area would generate an earthquake that would produce a tsunami,” said Rick Thomson, an oceanographer with the Institute of Ocean Sciences in Sidney, B.C.

Until then, researchers had expected that part of the Queen Charlotte fault to generate side-slipping earthquakes, as opposed to a wave-generating thrust quake.

Thomson and other scientists looked at how the Haida Gwaii tsunami waves affected the entire B.C. coast, and found that in certain Moresby Island inlets with a particular shape, the tsunami ran up to 13 metres high.

“I mean, it went all the way to Hawaii,” said Thomson.

“They received really big waves from this event.”

Haida Gwaii’s six-metre safety zone was chosen based on observations and modelling from the 2012 tsunami, but Thomson said it’s “one size fits all.”

“Six metres is really, in my opinion, a cautious number,” said Thomson, noting that planners on Vancouver Island and coastal areas of the Lower Mainland use three.

“Some of those areas in Haida Gwaii are just never going to be hit by tsunami waves they’re just too well protected.”

It is possible, but costly, to do more accurate modelling that would show the likely tsunami risk for each and every part of the Haida Gwaii coast.

Called inundation modelling, it requires high-resolution maps of the ocean floor as well as the land, since tsunamis are very sensitive to changes in water depth.

“Every site is different,” said Thomson.

“You go a kilometre down the road, from one bay to the next, and the tsunami response is going to be different.”

In the United States, inundation models have been done for every coastal community in California, Oregon, and Washington.

None has been done in B.C. yet, and the most likely places to start are the southern Vancouver Island and Lower Mainland areas at risk from a 9.0 or larger ‘mega quake’ in the Cascadia subduction zone.

“We’ve been pushing for it in Canada, but I guess our population density isn’t high enough, or the funds are just not there,” said Thomson.

“It’s an expensive proposition, but to do it correctly, it’s the only way.”

 

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