Brace yourself if you have family or friends living anywhere in the Columbia River valley. In the interest of public safety, we must raise grave concerns about landslide risks in the valley.
In July, a massive earthquake on the Eastern Russia Peninsula reminded us of the tectonic forces under our feet. The earthquake was followed by a tsunami and, a few days later, by a volcanic eruption in the same region. Ten days later, a 100 million cubic metre landslide came down in Alaska. Just the Earth doing its thing.
One of BC’s best-known landslides is the Hope Slide along Highway 3 in southern BC. The highway was rebuilt over the rubble, which came down on January 9, 1965. That same morning, two earthquakes were recorded nearby. The piece of mountain that slipped away that day is estimated at 45 million metric tons.
These unstable slide zones will continue to collapse over time.
BC mountains and valleys are crisscrossed by innumerable faultlines. The biggest is the Cascadia Fault off the coast of Vancouver Island. Another important faultline is the Columbia River Fault, where the Monashee Mountain Range pushes up against the Selkirk Mountain Range just west of the Rockies. At its top sits the Mica Dam, which holds back Lake Kinbasket.
The Revelstoke Dam, 70 kilometres south, holds back Lake Revelstoke near the city of Revelstoke. Both dams straddle the Columbia River Fault. Halfway between the two dams is the Downie Slide, with 70 metres of its toe under the waters of Lake Revelstoke. Its upper 3,000 metres are part of the Mount Katz massif on the Monashee side of the reservoir. Downie weighs in at 1.5 billion metric tons.
These unstable slide zones will continue to collapse over time. Concerned about public safety, BC Hydro engineers launched what may be the largest mountainside stabilization project on Earth. Using water drainage engineering, they increased the Downie Slide’s stability by 10%, although what that ultimately means is unclear.
Adding to the risk, another active landslide was discovered a few kilometres upstream from the Mica dam, The Little Chief Slide in the Mount Hallam Massif weighs in at 900 million metric tons. The danger of a new collapse tripled when a third active landslide was found on the Selkirks side of Lake Revelstoke in 2021. The St. Cyr Slide, only five kilometres from the Revelstoke Dam, is the same massive size as the Downie Slide.
A survey of downriver residents indicates few are aware of the dangers posed by these huge, active landslides. The biggest danger is that a new collapse in any of these slide zones could cause a tsunami violent enough to knock out the Revelstoke and/or Mica dams and scour the lower Columbia Valley, destroying the cities of Revelstoke, Castlegar, Trail, and every small town and dwelling along the way. Dismantling the Revelstoke and Mica dams might be the only way to prevent a wall of water racing downvalley after the collapse of one of these slides.
The safety issues raised here need to be brought to the public, not just discussed behind closed doors in government and corporate board rooms. All downstream residents should know the dangers lurking above the dams, and how their safety and wellbeing could be affected by another landslide collapse.
Donald Pharand is a researcher and eco-activist in the southeast of BC since the 1980s. don.pharand (at) gmail.com
