WHITEHORSE, YT – The Yukon Geological Survey has been able to assess the site of the Takhini River Landslide, and they’ve identified additional areas of instability along the top of the escarpment. They’ve also warned Yukoners to avoid the top and bottom of the slide area for now.
Derek Cronmillier, Head of Surficial Geology with the Yukon Geological Survey, confirmed that further landslides in the area are to be expected in near future as the slope around the most recent slide area stabilizes.
“So we have displacement of the surface above the slide, so we see cracks that will be several 10’s of centimeters wide, and extending for several meters along the top of the slope. That indicates that those portions bounded by those cracks are likely to fall in the near future. Large parts of the landslide head are actually overhanging, and those materials do not support overhanging slopes for very long.” – Derek Cronmillier, Head of Surficial Geology with the Yukon Geological Survey
Based on his assessment, Cronmiller says it’s likely the landslide last month didn’t have an acute trigger like snow loading or melt water, but was the result of a naturally occur process as the river slowly cut away the foot of the bank, destabilizing the slope above over time, with gravity eventually bringing it down.
“What I think happens here, is this is just a case of the slope getting steeper and steeper as the toe of the slope is eroded by the river. You have slow progressive deformation of an over-steepened slope on the banks… and you don’t need any sort of acute trigger for this to fail as a rapid landslide, it’s just gradual weakening of a slope overtime.” – Derek Cronmillier, Head of Surficial Geology with the Yukon Geological Survey
That process is common along the Takhini River, and Cronmiller notes it will continue for as long as the river remains.
Thanks to a report from a local property owner, the timing of the slide has now been pinpointed to December 17th.
