Disaster History of British Columbia

Earthquakes

The active subduction zone along the west coast of British Columbia is responsible for most of the ≈1,450 earthquakes each year in Canada, and most of the highest-magnitude events. In the 19th and 20th centuries, western Canada experienced eleven major earthquakes (magnitude 6.0 to 8.1). In the same time period, Quebec felt seven major earthquakes (magnitude 6.0 to 6.7), and Baffin Bay had an earthquake of magnitude 7.3.

Volcanoes

As part of the ring of fire, British Columbia has many volcanic areas less than 12,000 years old, although all are currently dormant. The ash of previous eruptions is useful for radiocarbon dating, while the ongoing threat of ashfall from explosive eruptions in Washington and Alaska pose a hazard through respiratory ailments, damage to infrastructure, and burial of crops.

Avalanches & Landslides

The mountain ranges are all young, high-relief regions, over-steepened by glaciation and currently subject to heavy precipitation, leading to avalanches and landslides. This is especially true of hydrothermally altered volcanics (Mount Meager), which are extremely weak, and downslope-dipping volcanics which have been truncated by glacial scour (Sea-to-Sky corridor).

Floods

The high relief also leads to flooding when heavy precipitation or rapidly melting snow are drained from the slopes into limited catchment basins, overwhelming rivers. Rivers in British Columbia are particularly prone to flooding after winters with higher-than-average snowfall, when sudden thaws and rapid melting quickly swell rivers. Outburst floods from landslide dams (1891 North Pacific Cannery and 1921 Britannia Beach) are also a concern.

Storms

Although the climate is generally more mild than that experienced in eastern Canada, hurricanes, flash floods, ice-jam floods, blizzards, hail, and windstorms regularly wreck mild havoc within British Columbia. Ice jams are a regular occurrence in the northern province, regularly threatening the community of Prince George and requiring evacuations. Severe weather includes the 1994 hailstorm near Salmon Arm causing $11 million in damage and the 1996 snowstorm in southwestern British Columbia dropping more than 100 cm of snow with damage estimated at $214 million. The largest fatalities from a single weather event occurred in 1962 when remnants of Typhoon Freda hit the Pacific coast, with windspeeds in Victoria reaching sustained speeds of 90 km/h with gusts to 145 km/h. The storm resulted in 7 deaths. Fog and icebergs are uncommon along the Pacific coast, as the ocean is temperate, and the temperature differences between land and sea are low. No significant tornadoes have been experienced in western Canada.

Tsunami

The tsunami and storm surge hazard is far higher in the Maritime provinces, but the outer coast of British Columbia (the west coast of Vancouver Island, and the northern coast of the mainland) is subject to tsunami and rogue waves, while the many fjords and lakes are vulnerable to local tsunami from landslides into confined water (1903 Upper Arrow Lake, 1905 Spences Bridge, and narrowly avoided in 1999 Eagle Pass). This is of particular concern along the many reservoirs formed by hydroelectric and storage dams, as overtopping and dam collapse may have downstream repercussions.

References

Mathews, B., & Monger, J. (2005). Roadside Geology of Southern British Columbia. Mountain Press Publishing Company.
McKinnon, M. (2010). Parameter Selection for Modelling Catastrophic Landslides. Master’s thesis, University of British Columbia.
Public Safety Canada (2007). Natural Hazards of Canada.
Transportation Safety Board of Canada (1997). Derailment Canadian National Train No. Q-102-51-26. Railway Occurrence Report R97V0063. 1997.

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