Water rise from Chilcotin River landslide may not be as high as feared: B.C. officials

A distant landslide successful B.C.’s Central Interior that’s blocking a stream is still being intimately monitored.

On Saturday afternoon, nan state issued an update, saying nan Chilcotin River landslide is still seeing activity arsenic immoderate debris continues to tumble down.

The authorities said this is expected, considering Wednesday’s landslide is still comparatively new.

Located astir 100 km southwest of Williams Lake, nan reservoir is estimated to beryllium 1,000 metres successful length, 100 metres precocious and 30 metres successful depth.

It besides said nan abrupt reservoir from pooling h2o down nan reservoir is continuing to turn astatine a complaint of 22 cm per hour.

Officials besides discussed worst- and best-case scenarios.

In nan worst-case scenario, h2o breaches nan apical of nan dam, pinch nan reservoir past failing 1 hr later.

The unreserved of h2o would beryllium instant and stunning, pinch nan Chilcotin River rising astir 10 metres.

A emblematic freshet travel during outpouring runoff successful nan Chilcotin River is astir 300 cubic metres per second. In this case, that would incredulously spike to 6,500 cubic metres per second.

Officials opportunity it would return that h2o 3 hours to unreserved down nan Chilcotin River and into nan Fraser River, wherever it empties.

At that confluence, this script would spot h2o unreserved into nan Fraser astatine astir 5,500 cubic metres per second. That equates to highest tallness being astir 4 metres higher supra their existent elevation.

Downstream astatine Lillooet, which would return 15 hours to reach, nan highest tallness would beryllium astir 1.8 metres supra h2o levels now. The travel location would beryllium astir 2,650 cubic metres per second.

“The bully news is that erstwhile we deed nan Fraser River, this h2o and worldly has a important magnitude of room to dispersed retired and disperse,” said Connie Chapman, who is pinch B.C.’s h2o guidance branch.

“To put this successful context, during a emblematic freshet twelvemonth (at Lillooet), we spot 5,400 cubic metres per second.”

At Hope, 29 hours later, nan h2o tallness would beryllium a 30-cm increase.

In nan best-case scenario, h2o will breach nan top, past return 24 hours to slow trim a transmission done nan dam.

At nan confluence of nan Chilcotin and Fraser, nan stream would only emergence 2.1 metres supra normal. And astatine Lillooet, it would beryllium nether a metre successful height.

However, officials warned that these are models pinch assumptions, and, sloppy if they’re correct aliases wrong, rushing h2o is very dangerous, nary matter really precocious aliases debased it is.

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“This really does springiness america a starting constituent to understand wherever we whitethorn beryllium headed,” said Chapman, adding nan state has assurance this will beryllium an over-the-top breach nonaccomplishment versus a seepage failure.

“As we proceed to cod data, we will beryllium capable to refine these numbers to springiness nan champion estimate we have.”

“The modelling now suggests that moreover nether those worst-case scenarios of a important breach happening rather quickly, h2o levels successful nan Fraser River mightiness beryllium only somewhat higher than what we would expect during a emblematic snowmelt season,” said Nathan Cullen, Minister of Water, Land and Resource Stewardship.

He added that while nan Chilcotin River faces existent risk, “we are not letting our defender down, moreover for a 2nd pinch regards to this issue. We proceed to actively show nan business and are preparing for each possibilities.

“There are still risks, including further landslides upstream of nan reservoir and imaginable slides downstream erstwhile nan h2o starts to travel done successful a important way.”

Cullen besides said it’s highly important for residents to obey emergency orders and to enactment distant from nan banks of nan Chilcotin and Fraser rivers.

“We are besides taking very earnestly nan imaginable effect of this descent connected chaotic salmon and different food species,” he said, adding that nan mostly of this year’s chinook salmon tally is past nan landslide area.

“We are besides estimating that we should person 4 to 7 days to scheme for returning sockeye salmon arsenic they activity their measurement up nan Fraser to nan Chilcotin.”

Bowinn Ma, nan Minister of Emergency Management and Climate Readiness, called it “an encouraging improvement for communities downstream.”

“But we nevertheless proceed to coordinate intimately pinch communities on nan rivers to guarantee that we’re prepared to protect group from imaginable flooding.”