British Columbia’s emergency management ministry said water is expected to start moving over the top of the massive landslide site currently blocking the Chilcotin River within hours.
Last Wednesday, an overnight landslide on the Chilcotin River created a dam across the river roughly 600 metres wide and 30 metres tall. Debris, like fallen trees, and water have been building up behind the landslide for days.
Since then, officials have warned that dam will fail.
Evacuation orders remain in place for about 100 square kilometres of land along the Chilcotin River, stretching from near Hanceville, B.C., to where the Chilcotin and Fraser rivers meet. The orders affect 13 residents, according to officials, and about 2,500 cattle.
In a statement Sunday, the ministry said it’s continuously monitoring the area, conducting aerial survey flights and gathering additional technical data.
“We are not letting our guard down even for a second,” said Nathan Cullen, B.C.’s minister of water, land and resource stewardship.
The ministry anticipates the water will start to move over the blockage late on Sunday or early on Monday, and enter the riverbed below the slide site.
The water level behind the natural dam has been rising steadily since the landslide at a rate of about 18 centimetres per hour.
According to current estimates, it will take 12 to 24 hours for the water to pass through the blockage. This will cause water flow to be about 10 times higher than usual in the Chilcotin River but lower than typical spring runoff Fraser River.
The ministry says a worst-case scenario could involve a rapid draining of the slide site, which could result in a 21-metre rise of the Chilcotin River near the Farwell Canyon Bridge.
On Sunday evening, B.C.’s River Forecast Centre issued an upgraded flood warning, signalling water levels are expected to rise past river banks imminently for the Chilcotin River downstream of the landslide near Farwell Canyon.
“This situation is very dynamic, and I want to be clear that the valley could be extremely unstable and dangerous,” B.C. Emergency Preparedness and Climate Change Minister Bowinn Ma said during a press conference on Saturday.
The province launched a new Chilcotin River landslide information portal on Sunday afternoon to share the latest information about the slide with the public.
The ministry says risks to public safety include the potential for further landslides upstream of the natural dam and downstream of the dam once water begins to flow past it.
The peak flow could take up to 13 hours to reach Lillooet, B.C., according to the province. Ma said several patients have been relocated away from health-care centres in Lillooet, in case floods lead to an emergency situation there.
B.C. residents, the provincial government and First Nations are bracing for a possible deluge of water after a massive landslide dammed the Chilcotin River in B.C.’s Cariboo region. Officials warn ‘impacts could be significant’ if the slide gives way.
The minister added several residents have been seen returning to the evacuated zone to look at the landslide and fly drones in the area.
“Operation of any aircraft that is not part of the landslide response is illegal in this area,” Ma said. “This is extremely dangerous, and poses a threat to both the people that re-enter the area and the experts assessing the situation on the ground.”
The minister urges people to heed evacuation orders and alerts and stay away from the river areas.
Missing dog found
One camper was caught in the landslide, according to paramedics. On Wednesday morning, he was rescued and airlifted him to Williams Lake, B.C., where he was taken to hospital.
The man was separated from his dog, Seiko, in the landslide.
Gerald Pinchbeck, with the Cariboo Regional District’s emergency operations centre, told CBC News on Friday that Seiko had been spotted along Highway 20 and has since been reunited with his owner in Williams Lake.
“We had our hearts out and thoughts out hoping that this dog would make it through,” Pinchbeck said. “We’re very relieved that he did.”