A landslide along the Chilcotin River near Williams Lake, B.C., is shown in this recent handout photo. Flooding is a major concern after a landslide blocked the Chilcotin River in British Columbia's Interior. Photo: Central Cariboo Search and Rescue.
A massive amount of debris piled 30 metres high from a landslide has dammed the Chilcotin River in British Columbia’s central Interior, creating a lake that a regional official says could give way within the next 24 to 48 hours.
Margo Wagner, chair of the Cariboo Regional District, says water building up behind the slide south of the City of Williams Lake could reach a level where it will start flowing over the debris, or it will erode the material, causing it to give way.
“As the water continues to flow and builds up behind that landslide, the pressure increases, but we do not have a definitive time of when that will let go,” she told a media briefing on Thursday.
Wagner said the riverbed below the slide is dry, and officials aren’t certain about the potential downstream impacts when the dam is breached.
But she said it’s clear there would be “a mass of water” coming down the Chilcotin, which flows south into the Fraser River.
Evacuation orders span 107 square kilometres along the Chilcotin, with officials saying the slide poses an “immediate danger to life and safety.”
The district says 60 properties are covered by the orders, including 12 homes with an estimated 13 residents.
The slide is “massive,” Wagner said, with material piled 30 metres high and stretching 600 metres in length, blocking the flow of the Chilcotin.
She said it happened in an area that was “burned out” during wildfires in 2017.
“There is a lot of area (where) the trees are dead. They are still standing, but their root system is totally done, and they are not absorbing water, which is an issue.”
Wagner said regional officials weren’t aware of any injuries except to one man who broke his leg while he was running away from the slide, which struck late Tuesday or early Wednesday.
Debra Bortolussi with Central Cariboo Search and Rescue said the man had set up camp for the night during a rafting trip, and he woke up to the sound of the slide.
She said he managed to run to safety as the ground moved beneath his feet, but his dog is missing.
“It directly came down overtop of where he was,” Bortolussi said in an interview Wednesday. “His tent, his raft, everything was taken out by the landslide itself.”
The B.C. government issued a statement saying the sudden release of the blockage could cause “rapid rises” in downstream water levels.
The province has warned people to stay away from the banks of the Chilcotin River below the slide all the way down to the Fraser River north of Hope, about 150 kilometres east of Vancouver.
B.C.’s River Forecast Centre has issued a flood warning for the Chilcotin north of the slide, saying the debris is “creating a lake” that extends several kilometres upstream.
The forecast centre says the eventual breach of the landslide debris could also lead to an “outburst flood” with a surge of water rapidly flowing downstream.
If that happens, it says the surge could reach the Fraser River within hours, and while flooding south of the Fraser Canyon would likely be less severe, substantial increases in flow could extend to the mouth of the river in Metro Vancouver.
The provincial statement says the Ministry of Emergency Management is working with communities to co-ordinate response operations, and the BC Wildfire Service has dispatched helicopters to help with assessments and potential rescues.
“The province is prepared to take additional actions to keep people and communities safe in the event of flooding, such as deploying sandbags, sandbag machines, gabions and tiger dams to communities if needed,” it says.
