Concerns for wild salmon in wake of Chilcotin River landslide
August 7, 2024
By: Dene Moore
A massive debris dam that blocked the Chilcotin River following a landslide last week has given way but the fallout is far from over.
The Tŝilhqot’in National Government, in whose territory the Chilcotin – or Tŝilhqox – River flows, has formed an emergency salmon task force and called on all levels of government on both sides of the border, including specifically Alaska, to cease fisheries that may impact Fraser watershed stocks.
A massive landslide July 30 resulted in a debris dam that blocked the Chilcotin River, a tributary of the Fraser. Photo courtesy Tŝilhqot’in National Government.
“Increased sediment, debris, and flow to the Tŝilhqox and ʔElhdaqox (Fraser River) have and will continue to have dramatic impacts on this year’s sockeye and chinook runs,” the Tŝilhqot’in said in a statement.
The nation called on all First Nations downstream, the Pacific Salmon Commission and neighbouring U.S. states to take measures to conserve Chilcotin-bound salmon until the impacts of the landslide are known. Watershed Watch has long raised concerns about the devastating toll southeast Alaska’s interception fisheries have on depleted B.C. salmon stocks.
“Salmon are the main food source for our people,” said Tribal Chair Joe Alphonse. “We need long-term alternative solutions to the salmon stocks. We also need full rehabilitation of our fishing sites and must look at stabilizing the upstream and downstream areas. There will be a lot of work ahead of us.”
The July 30 landslide happened about 30 kilometres upstream of the confluence of the Fraser and Chilcotin rivers. A debris field of trees and earth estimated to be a kilometre long, 600 metres wide and 30 metres deep completely blocked the river.
The river formed a lake behind the debris dam that eventually overflowed the blockage and quickly flushed the mostly sandy debris out of the river’s path.
It’s not the first time the watershed has been affected by landslides, points out Greg Taylor, fisheries expert, consultant and advisor to Watershed Watch. Massive slides occurred at Hell’s Gate in the Fraser Canyon in 1914 and another at Big Bar in 2019.
“Indigenous knowledge, archeological evidence, and recent history indicate these types of events are normal and to be expected,” Taylor says. “Salmon have survived them over the past 10,000 years due to the species diversity and abundance.”
However, salmon no longer have that species diversity and abundance that historically provided a buffer to such natural disasters.
“Climate change on top of development, poor land management, commercial, recreational, and IUU (illegal, unreported and unregulated) harvesting over the past 100 years have eroded both the diversity and abundance of salmon, rendering them much more vulnerable to these events,” Taylor says. “We see this with the current slide. Even before the slide, water temperatures and levels at Hell’s Gate in the Fraser Canyon were approaching lethal levels for salmon relative to historical norms.”
The landslide upstream on the Chilcotin reduced flows and pushed temperatures up even more. That potentially delayed or compromised the migration of salmon, many of them from threatened or endangered populations.
It’s not just Chilcotin sockeye that are affected. There are 43 other sockeye populations, chinook, coho, and steelhead, as well.
This photo taken from a helicopter shows the Chilcotin River slide area after the river breached the debris dam August 5. Photo courtesy Tŝilhqot’in National Government.
“These delays, or spending any time in temperatures above their lethal threshold, will risk salmon’s ability to successfully spawn. Remember, these salmon quit eating weeks ago. The time window for them to pass through the Fraser River and into their natal streams is exceedingly short before they will die without successfully spawning,” Taylor points out.
So even though the slide has resolved itself quickly, the effect will be long lasting, he adds.
“Decreased flows and increased temperatures will take time to come back to where they were before the slide, which we were already at levels dangerous to salmon. Add to this the impact of the debris and sediment discharge from the slide and how it will change salmon habitats, this slide will be impacting salmon long after it leaves the current news cycle.”
Natural disasters like this slide are bound to happen, Taylor says.
“We need to quit killing wild salmon to rebuild their abundance and diversity to rebuild, as best we can, the natural buffer this provides them so that they can survive inevitable calamities like the current slide.”
While fears of flash flooding downstream with the dam’s breach did not play out, it’s a reminder of how much work has yet to be done for B.C. and the Lower Mainland to be prepared, says Lina Azeez, Watershed Watch’s habitats program director.
“We are lucky the downstream impacts on our built environments will be minimal this time. We are certainly not prepared to face another major flood just 2 1/2 years after the last one,” she says. “As those who live downstream of the largest river in B.C., we need to better understand what we are dealing with and build a floodplain that can bounce back after an inundation.”
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Concerns for wild salmon in wake of Chilcotin River landslide
August 7, 2024
By: Dene Moore
A massive debris dam that blocked the Chilcotin River following a landslide last week has given way but the fallout is far from over.
The Tŝilhqot’in National Government, in whose territory the Chilcotin – or Tŝilhqox – River flows, has formed an emergency salmon task force and called on all levels of government on both sides of the border, including specifically Alaska, to cease fisheries that may impact Fraser watershed stocks.
A massive landslide July 30 resulted in a debris dam that blocked the Chilcotin River, a tributary of the Fraser. Photo courtesy Tŝilhqot’in National Government.
“Increased sediment, debris, and flow to the Tŝilhqox and ʔElhdaqox (Fraser River) have and will continue to have dramatic impacts on this year’s sockeye and chinook runs,” the Tŝilhqot’in said in a statement.
The nation called on all First Nations downstream, the Pacific Salmon Commission and neighbouring U.S. states to take measures to conserve Chilcotin-bound salmon until the impacts of the landslide are known. Watershed Watch has long raised concerns about the devastating toll southeast Alaska’s interception fisheries have on depleted B.C. salmon stocks.
“Salmon are the main food source for our people,” said Tribal Chair Joe Alphonse. “We need long-term alternative solutions to the salmon stocks. We also need full rehabilitation of our fishing sites and must look at stabilizing the upstream and downstream areas. There will be a lot of work ahead of us.”
The July 30 landslide happened about 30 kilometres upstream of the confluence of the Fraser and Chilcotin rivers. A debris field of trees and earth estimated to be a kilometre long, 600 metres wide and 30 metres deep completely blocked the river.
The river formed a lake behind the debris dam that eventually overflowed the blockage and quickly flushed the mostly sandy debris out of the river’s path.
It’s not the first time the watershed has been affected by landslides, points out Greg Taylor, fisheries expert, consultant and advisor to Watershed Watch. Massive slides occurred at Hell’s Gate in the Fraser Canyon in 1914 and another at Big Bar in 2019.
“Indigenous knowledge, archeological evidence, and recent history indicate these types of events are normal and to be expected,” Taylor says. “Salmon have survived them over the past 10,000 years due to the species diversity and abundance.”
However, salmon no longer have that species diversity and abundance that historically provided a buffer to such natural disasters.
“Climate change on top of development, poor land management, commercial, recreational, and IUU (illegal, unreported and unregulated) harvesting over the past 100 years have eroded both the diversity and abundance of salmon, rendering them much more vulnerable to these events,” Taylor says. “We see this with the current slide. Even before the slide, water temperatures and levels at Hell’s Gate in the Fraser Canyon were approaching lethal levels for salmon relative to historical norms.”
The landslide upstream on the Chilcotin reduced flows and pushed temperatures up even more. That potentially delayed or compromised the migration of salmon, many of them from threatened or endangered populations.
It’s not just Chilcotin sockeye that are affected. There are 43 other sockeye populations, chinook, coho, and steelhead, as well.
This photo taken from a helicopter shows the Chilcotin River slide area after the river breached the debris dam August 5. Photo courtesy Tŝilhqot’in National Government.
“These delays, or spending any time in temperatures above their lethal threshold, will risk salmon’s ability to successfully spawn. Remember, these salmon quit eating weeks ago. The time window for them to pass through the Fraser River and into their natal streams is exceedingly short before they will die without successfully spawning,” Taylor points out.
So even though the slide has resolved itself quickly, the effect will be long lasting, he adds.
“Decreased flows and increased temperatures will take time to come back to where they were before the slide, which we were already at levels dangerous to salmon. Add to this the impact of the debris and sediment discharge from the slide and how it will change salmon habitats, this slide will be impacting salmon long after it leaves the current news cycle.”
Natural disasters like this slide are bound to happen, Taylor says.
“We need to quit killing wild salmon to rebuild their abundance and diversity to rebuild, as best we can, the natural buffer this provides them so that they can survive inevitable calamities like the current slide.”
While fears of flash flooding downstream with the dam’s breach did not play out, it’s a reminder of how much work has yet to be done for B.C. and the Lower Mainland to be prepared, says Lina Azeez, Watershed Watch’s habitats program director.
“We are lucky the downstream impacts on our built environments will be minimal this time. We are certainly not prepared to face another major flood just 2 1/2 years after the last one,” she says. “As those who live downstream of the largest river in B.C., we need to better understand what we are dealing with and build a floodplain that can bounce back after an inundation.”
