New report outlines Mount Currie landslide risk 

Low risk of major landslide; public info sessions set for Jan. 24, 25

click to enlarge SHUTTERSTOCK PHOTO BY HARRY BEUGELINK - RISK ASSESSMENT An assessment of landslide risk on Mount Currie found a low risk of a major slide, but engineers recommend ongoing monitoring.
  • Shutterstock photo by Harry Beugelink
  • RISK ASSESSMENT An assessment of landslide risk on Mount Currie found a low risk of a major slide, but engineers recommend ongoing monitoring.

A new report outlines the risk of landslides on Mount Currie.

Undertaken by BGC Engineering Inc., "The Mount Currie Landslide Risk Assessment" determines that areas of instability could lead to small rockfall events and rare — but large-scale — rock slope failures.

The report's authors identified two scenarios in which large slides would travel north of the Green and Lillooet Rivers and cause flooding and damage to structures. Under the scenarios, the rockfalls would travel over 100 kilometers per hour and involve volumes of up to 8 million cubic metres of material.

The probability of the scenarios occurring, however, is low, according to the report. The calculated annual probability of the two scenarios is .02 per cent and .0009 per cent, respectively.

Fifteen properties in the affected areas are assessed as being at direct risk from the rockslides, including private property and infrastructure such as the Pemberton Regional Airport and Wastewater Treatment Plant. Associated flooding would affect 160 buildings.

"As local government organizations, we want to continue to monitor and understand if that low likelihood of a major rockslide event is changing," explained Squamish-Lillooet Regional District Chair Jack Crompton.

According to the report, Mount Currie's stability is influenced by the existence of permafrost, which is being degraded due to global warming.

"Projected climate change is expected to further deteriorate rock-slope stability, but how this might increase rock avalanche probability in the future cannot be reliably quantified due to the unknown distribution of permafrost and strength reduction associated with loss of ice cohesion in the rock mass," said the report.

Because of the size of the area, BGC said engineered mitigation options are not practical and recommends ongoing monitoring. The assessment also recommends that land use be restricted in areas modelled for rock avalanches.

The full report can be found at https://www.pemberton.ca/public/download/documents/47160

Elected officials and staff from Lil'wat Nation, the SLRD and Village of Pemberton will be hosting two community information sessions next week. Each session will include a presentation by BGC Engineering, followed by a question and answer period.

The sessions will be held on Wednesday, Jan. 24 at the Pemberton & District Community Centre from 6:30 p.m. to 8:30 p.m., and Thursday, Jan. 25 Ull'us Community Complex from 6:30 p.m. to 8:30 p.m.

Pick up next week's Pique for more.

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