Some B.C. lakes could be at risk of tsunamis, says SFU prof

Landslides that enter lakes can cause massive waves similar to earthquake-triggered tsunamis in the ocean.

Earth sciences professor points to Salmon Arm as example of place that could be at risk

Salmon Arm is located right next to Shuswap Lake. (csrd.bc.ca)

It's not just oceanfront communities that are at risk of damage from tsunamis, says a Simon Fraser University professor. So too are communities located next to some inland lakes.

And B.C. is home to a number of these lakes, according to earth sciences professor John Clague, who points to Salmon Arm as an example of a city that could potentially be at risk.

"Most sort of look to the oceans when we think of tsunamis," Clague told Daybreak South host, Chris Walker.

"But we know that we can get tsunamis, or at least displacement waves, triggered by landslides that enter lakes or the inlets along our coasts."

Chehalis Lake landslide

In December of 2007, a large landslide entered Chehalis Lake near Mission. It produced waves that reached a height of 30 metres and ran the entire eight-kilometre length of the lake.

"All along the lake, it just stripped off all the forest, all the vegetation, left it bare," he said.

That incident happened at a time when no one was camping next to the lake, but had it happened in the summer, dozens of campers would have died, said Clague.

These kinds of incidents are not common in B.C., but the province does have a history of them going back to the 19th century.

"We have thousands of kilometres of shoreline. There are a lot precipitous slopes bordering our lakes," said Clague. "There is a possible danger to some of our communities that are built right down to the shores of these lakes."

Salmon Arm

Salmon Arm is a community that fits that description. It is built right to the shore of Shuswap Lake. On the other side of the lake are a number of large rock walls.

"I don't know that they're unstable. They may be totally stable, but given the history we've had, I think it would be wise for us to at least consider the possibility and look for evidence of instability along the steep walls of Shuswap Lake," said Clague.

Clague said that in Norway the government has a monitoring program using satellites that can detect tiny movements of slopes near lakefront towns.

"These would be movement of slopes of millimetres per year. If you can detect those movements on a steep slope, then you might have a concern because that indicates a slope is unstable and potentially could fail in a landslide."

Clague would like to see governments here adopt a similar program.

You wouldn't have to monitor every lake in the province. It wouldn't be realistic to do that. What I would do is prioritize communities where there potentially could be a problem," he said.

"I just highlighted Salmon Arm, not because there is an imminent problem. It's just a community that I think would want to do this monitoring."

With files from CBC Radio's Daybreak South