Lake tsunamis are a real and dangerous threat that an SFU professor believes British Columbians need to be more aware of.
According to John Clague, an SFU professor in the department of earth sciences, “The public and other government agencies don’t seem to be aware that this is a hazard that is potentially a deadly one.”
Clague became interested in this research after observing the consequences of the 2007 landslide into Chehalis Lake. The impact of the unstable shoreline hitting the water caused a wave that exceeded 30 metres.
If this event had occurred in the summer months when individuals had been camping along the lake, Clague asserts that it could have resulted in deaths. “If that had happened in July it could have killed 50 people!” he exclaimed.
When landslides cause lake tsunamis, the waves they create spread away from the point source much in the same way as they do when “throwing a pebble into a pond.” However, these waves can be very large, and have the potential to do a lot of damage.
These are distinct from the tsunamis caused by earthquakes that affect large areas and travel far distances. The effects of landslide tsunamis are highly dependent upon location. As Clague explained, “A big enough landslide falling at a high enough speed can produce very, very large waves, but they diminish faster away from the source”.
The 1958 tsunami in Alaska — the largest in modern history — was actually the result of a landslide that was triggered by an earthquake. The landslide drove a wave into Lituya Bay that ran 518 metres up the opposite slope of the inlet, stripping the old growth forest.
British Columbia contains many lakes and extensive fjords along its coastline that put it at a particularly high risk for this type of tsunami. In Norway, where there is a similar coastal geography and a more densely populated coastline, landslide-triggered tsunamis have lead to more than 100 deaths this past century.
With increasing coastal populations in British Columbia, Clague explained, “We need to look at our coastlines and look at our lake shorelines, and identify areas where there might be a hazard. Right now, we just don’t know.”