B.C. Insider: Landslide resculpts Chilcotin River, imperils salmon runs

Good morning,

The satellite image of the Chilcotin River at Farwell Canyon taken late last week looked like a blue doodle stopped mid-stroke. The image shows the river flowing in a lazy, icy-coloured wend, through a rugged mountain pass. And then it ends abruptly, the riverbed on the other side so dry that it was barely an outline.

Tonnes of earth broke free of the bank and spilled into the river, stoppering it and creating a new, 11-kilometre lake. The dam caused by the slide was massive – a kilometre long, 600 metres wide and 30 metres deep.

But over six days, there was no catastrophic break in the dam and fears of a sudden, gushing flood of water were abated as the water level in the lake rose to the dam’s height, spilling over and carving a 15-metre channel into the dam, officials said Monday.

As the water spilled over to the dry side, emergency officials issued evacuations orders and alerts aimed at keeping people away from the banks of the Chilcotin and Fraser Rivers. While only about a dozen properties are affected, Emergency Management Minister Bowinn Ma said the water breaching the dam caused by the slide will cause river bank instability.

Evacuation alerts and orders along the rivers are not just about residential properties, she said.

“It is also about people recreating on the water or along the waterways,” Ma said at a briefing Monday. “We need people to leave those areas, to not put their boats down, to not go down to take a look at the water, to not engage in recreation activities anywhere along the Chilcotin River or the Fraser River right now.”

Among structures officials are watching is the Farwell Canyon Bridge, about 22 kilometres downstream, she said.

It’s a much preferable outcome to the worst-case scenario feared last week. The slide held the potential to cause catastrophic flooding for the communities downstream if the dam created by the wall of earth suddenly ruptured, gushing water and debris down to the Fraser River. Communities as far away as Hope were told to be on alert and prepared to leave at a moment’s notice.

Ms. Ma, who had spent part of the week before delivering briefings about forest fires, told reporters repeatedly Thursday the situation was “dynamic,” carrying a risk “that has the potential to be significant.”

But it says something about the vastness of British Columbia that only 12 homes with an estimated 13 residents were initially ordered evacuated. One man who was camping with his dog felt the earth move, but managed to escape. (The man was rescued, the dog was found days later.)

By Friday, officials were less worried that the dam would rupture and instead had concluded the water would spill overtop of the dam and in the process, flush the silty dam away over a matter of days. That process began Monday.

In an explanatory piece, Patrick White reported the earthen landslide poses not nearly the same threat as the rockslide of 2019 on the Fraser River, which blocked salmon runs and required blasting to clear.

Tl’etinqox Chief Joe Alphonse, who also represents five other local nations as tribal chairman of the Tsilhqot’in National Government, said that in Tsilqot’in, that stretch of the Chilcotin is known as Nagwentled, or ‘landslides across the river’ – its shifting geography prophesized in language.

Although there appears to be no human catastrophe resulting from the slide, the river will resculpt itself, carving a new path over, around or through the mass of sand and trees as it flows towards the Fraser River.

It’s also unclear how the slide will affect the pending salmon run, a major concern for area First Nations.

“This will take time,” Mr. Alphonse said.

This is the weekly British Columbia newsletter written by B.C. Editor Wendy Cox. If you’re reading this on the web, or it was forwarded to you from someone else, you can sign up for it and all Globe newsletters here.