B.C. officials urge residents to prepare for the worst as landslide blocks major river, raising fears of flooding

Open this photo in gallery:

People along B.C.’s Fraser and Chilcotin rivers are being warned to leave the area immediately over fears that a massive landslide that has dammed the Chilcotin River could give way, sending a torrent of water and debris downstream. Communities as far south as Hope were put on alert Thursday as emergency-management officials urged residents to prepare for a worst-case scenario.

“If this dam were to break, it is possible that dozens of evacuation orders and alerts will be issued along both rivers, and people need to be prepared,” Bowinn Ma, B.C.’s Minister of Emergency Management, said at a media briefing. “The risk to people and communities along the river is unknown at this time, but it has the potential to be significant.”

Ms. Ma said the BC Wildfire Service has deployed aerial support, search-and-rescue crews have helped to evacuate people from the area and geotechnical assessments and modelling are under way. The province is also prepared to take additional measures such as deploying sandbags, sandbag machines and Tiger dams – water-filled flood-barriers – to communities as needed, she said.

Williams

BRITISH

Lake

COLUMBIA

Area of landslide near

Farwell Canyon

Area under

flood watch

Kamloops

BRITISH COLUMBIA

Kelowna

Courtenay

Hope

Vancouver

Vancouver

Island

UNITED STATES

50 km

Williams

BRITISH

Lake

COLUMBIA

Area of landslide near

Farwell Canyon

Area under

flood watch

Kamloops

BRITISH COLUMBIA

Kelowna

Courtenay

Hope

Vancouver

Vancouver

Island

UNITED STATES

50 km

Williams

BRITISH

Lake

COLUMBIA

Area of landslide near

Farwell Canyon

Area under

flood watch

Kamloops

BRITISH COLUMBIA

Kelowna

Courtenay

Hope

Vancouver

Vancouver

Island

UNITED STATES

50 km

Nathan Cullen, B.C. Minister of Water, Land and Resource Stewardship, said the landslide is approximately 600 to 800 metres in length, 600 metres across and 30 metres deep. The pooling water has formed a lake that is roughly eight to 10 kilometres long.

Mr. Cullen said the government is working with experts and local communities “to understand if a slower release of water is imminent or possible in a natural way, or through other interventions.”

The landslide occurred late Tuesday night, resulting in a blockage of the Chilcotin River near Farwell Canyon, a remote area in the central B.C. Interior. The province issued an emergency alert on Wednesday, saying sudden potential flooding and debris flow could pose a threat to human life. It directed people and boaters to immediately leave the banks of the Chilcotin River from Hanceville to the Fraser River, and from the banks of the Fraser River from the Chilcotin River to Hope.

Ms. Ma said while it appeared that the landslide had resulted in a complete blockage on Wednesday, on-site monitors reported some water seepage through the area on Thursday.

“Of course, the Chilcotin River is also fed by many other tributaries,” she said. “It is possible that the water is finding its way elsewhere.”

Only one injury has been reported. A man camping along the Chilcotin River with his dog awoke to the sound of the slide on Tuesday night and ran to safety as the ground moved beneath his feet, according to Central Cariboo Search and Rescue. The man was treated in hospital; his dog has not yet been located.

B.C.’s River Forecast Centre has issued a flood warning for the Chilcotin River north of the slide, meaning river levels have exceeded or will exceed the top of its banks imminently, and a flood watch downstream, meaning river levels will approach or may exceed its banks.

Evacuation orders span 107 square kilometres along the Chilcotin. The Cariboo Regional District says 60 properties are covered by the orders, including 12 homes with an estimated 13 residents.

Dwayne Tannant, a professor in the School of Engineering at the University of B.C., reviewed images of the slide on Wednesday and said water levels could rise for about a week before overtopping the dam. He said the province likely issued warnings reaching as far south as the Fraser Valley out of an abundance of caution.

“You’d probably see the water rise a little bit at Hope,” he said. “I don’t think it’s going to be catastrophic or anything, but nobody knows for sure.”

Connie Chapman, executive director of the water management branch in the Ministry of Water, Land and Resource Stewardship, said the area saw landslides in 2004 and 1964, but “definitely not to the scale and scope” of this week’s event.

Cariboo Regional District chair Margo Wagner said geotechnical, hydrology and engineering teams from the province are assessing the situation.

“It’s hard to give a definitive timeline [but] the province now has boots on the ground actually out in the area,” she said in an interview Thursday afternoon.

Open this photo in gallery:

Ms. Wagner said the landslide comprises a mixture of sand and silt, making it vulnerable to erosion. The district is working closely with Indigenous partners, whose involvement is crucial, given that it is salmon-spawning season and there are significant archeological sites along the river, she added.

Williams Lake First Nation Chief Willie Sellars said his community was concerned about the impact of the slide on culturally significant sites, such as villages and burial grounds, and on the salmon run. The Big Bar landslide of 2019, north of Lillooet, trapped migrating salmon and had an impact that lasted years.

“We can only hope that our prayers will be answered and the fish are able to make it through this natural disaster,” he said.

But “it’s not just about the land and the fish and areas of cultural significance to our people. It’s also about the mental health and wellness of our people.”