At least 4,000 people in and around the village of Pemberton, B.C., are facing the prospect of evacuation due to a massive landslide Friday that has blocked Meager Creek at the confluence with the Lillooet River, raising the spectre of flooding as the waterway backs up.
Jordan Sturdy, mayor of the village about 250 kilometres north of Vancouver, said an evacuation alert was in the works, but may or may not proceed to a full-fledged relocation of residents.
"It will stretch our resources, there's no question about that," he said in an interview. Referring to Whistler, which helped play host to the 2010 Winter Olympics, he added: "We'll certainly look to our neighbour in the south, who I trust are not running at full occupancy at this time."
He said residents are being asked to be aware of a possible call for evacuation - a first in the 20 years he has been a resident of Pemberton, even though the area of Friday's event has been deemed one of the most slide-prone in Canada.
"The avalanche has blocked off the free flow of the Meager River and so it's impounding the river behind an earthen dam," said John Clague, an earth sciences professor at Simon Fraser University. "Essentially there's no flow coming out of the Meager Creek drainage. A lake has been created and the earthen berm could fail and, depending how it fails, it could have an impact."
Mr. Sturdy said he was hard-pressed to offer a projection on the time frame. "The berm or the dam could breach or fail in minutes to hours to days. It's hard to know."
He said an actual evacuation alert would be transmitted by radio, social media and door-to-door knocking.
Mr. Sturdy said options for clearing the mix of soil, rock and snow in the slide are limited by the lack of stability in the area. "It wouldn't take much to drop another million cubic metres of the face of the peak of that slide."
He noted that the provincial Forestry and Environment ministries are assessing the situation. "[They]will be making further recommendations to us," he said.
Marty Van Loon, a farmer, said he is watching the situation carefully, looking for rising water levels. "We know it's a risky area up here because it has happened three or four times in the past," he said.
Friday's incident forced the evacuation, by helicopter, of 13 campers who were trapped by the slide. All were rescued safely. No injuries have been reported.
Prof. Clague said there have been six such slides at the site of Friday's incident since 1931. The most recent was in 2009.
"This landslide is big, but not unique," he said. "The area is prone to slides. It's a dormant volcano with high, fractured lava leading to rocks that are prone to slides. That, with deep slopes, is a recipe for slides."
RCMP Sergeant Shawn LeMay of the Whistler detachment said in an interview that police received a report of the landslide at about 6:50 a.m..
"It was a large avalanche that fell down, right on the water flow," he said. "That has created a natural dam. We're asking people to stay out of the area if they were planning on hiking or doing some recreational camping in the area - if they could find an alternative location for the weekend as we continue collectively to assess the damage here."
Ian Indridson of the province's Public Safety Ministry said police and search-and-rescue personnel launched the evacuation of the campers after the slide. He said officials from the ministries of Environment and Forests will assess the slide and determine whether road closings or further public safety warnings are needed.