Residents of a small British Columbia community where a landslide destroyed several houses and killed four people this summer have been warned another threat is hanging over them.
A team of geotechnical experts probing the cause of the massive slide that hit Johnsons Landing has found fracture lines in the mountain above the rural area, where 33 people live, 70 kilometres northeast of Nelson.
"Geotechnical experts do estimate that another slide could run as far as, if not further than, the most recent slide," states an information bulletin distributed Tuesday by the Central Kootenay Regional District. "This means that all properties at the edge of the slide and in front of the slide currently under evacuation order are still considered at high risk due to the landslide hazard."
The bulletin says a 300,000-cubic-metre block of material has shifted on the mountain slope, near where the first slide originated.
But Frances Maika, of the district's Emergency Operations Centre, said it is impossible to know when – or even if – the second slide will be occur.
"It's a very dynamic situation. You can't predict when. You can just say these are the hazards, this is the level of the hazard and these are the time periods when the hazard is likely to be highest," she said.
The July 12 slide was triggered when a late snow melt coincided with heavy rains, saturating soil. Ms. Maika said that is likely what would cause the next block to come tumbling down, too.
"The geotechs know the highest risk period is the [runoff]. So that is next spring, and I guess any unusual rain event that might occur between now and then," she said.
Ms. Maika said one-on-one meetings are planned with residents so they can be apprised of the specific threat to their property. Although 33 people live in Johnsons Landing, some of them are there only seasonally, and some have homes outside the slide zone.
Ms. Maika said 12 properties are directly in the slide zone, which remains under evacuation order.
Richard Ortega, who runs Johnsons Landing Retreat Center, said his home is well outside the slide zone and he feels safe despite the recent caution by the geotechnical field team.
"The geotechs actually stayed here at the Retreat Center, when they were doing their research. And nobody came in wringing their hands, looking like the mountain was about to fall down or anything, so I think there's a bit of [media] sensationalism out there," said Mr. Ortega.
He said the first slide cut a deep trough when it came roaring down Gar Creek, and he feels if the remaining block comes down, it would likely stay in that channel.
But Gregory Utzig, who has a recreational cabin in Johnsons Landing, said the latest report clearly shows there is continuing risk of a slide impacting the community.
"I think everyone knows that next spring when snow melt occurs there's going to be significant risk again. The question is whether this big chunk will be mobilized or not … you know, it could come down this spring or it could come down in 100 years."
In addition to the research being done in Johnsons Landing, the provincial Ministry of Forests is conducting a wider review. In an e-mail, Forests Minister Steve Thomson said he has asked staff to determine if changing weather patterns are increasing the frequency of slides, to find better ways to predict events and to look at the practicality of installing protective structures in some communities. That report should be ready in a few weeks.