Bad Day Fishin’
It is said that “A bad day of fishing is better than a good day of work”. I won’t argue, but if you were trolling for trout at Chehalis Lake, British Columbia on December 4, 2007, you’d have had a bad day. Chehalis Lake, 50 miles east of Vancouver is a lovely spot nestled in the mountains. Prior to that date, it was known mostly to fisher folk and 4 wheel drive enthusiasts.
That all changed when 3 million cubic meters of rock fell from a slope 500 meters above and struck the still water. Some 40 meters tall at birth, a tsunami burst out over the Lake. The wave washed the shoreline clean of trees and brush, and probably beached a few striped bass to the delight of local bears. Four minutes later, a six meter wave reached the far south shore, seven km distant.
Scientists visited the site soon after and made detailed measurements of the flow heights and directions. Their information helped me create this computer simulation of the landslide and lake tsunami.
Rockfall or landslide-induced waves in confined water bodies, rivers, and fiords are not uncommon. I’ve blogged here before about several cases: Yangtze Tsunami, Swiss Tsunami, Vaiont Flood Disaster. Constricted waterways sometimes amplify and prolong wave motions. Wave hazards have to be recognized by designers and owners of water-level facilities where potential for lake tsunami exists. Such potential may not take expert opinion to judge. If from the seat of your boat, towering cliffs and mountains surround, you got potential.
The roads to the Lake, I understand, are barricaded now as authorities still consider the area to be dangerous to people. Could be, but with fewer hanging hooks about, Chehalis fish can swim easy.
Steven N. Ward Santa Cruz
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John Rundle is a Distinguished Professor of Physics and Geology at UC Davis and the Executive Director of the APEC Collaboration for Earthquake Simulations. He chaired the Board of Advisors for the Southern California Earthquake Center from 1994 to 1996. Read John's blog.