T85 Landslide Hazards: Inventories, Hazard Maps, Risk Analysis, and Warning Systems (Posters)

Monday, 11 October 2021
9:00 AM - 1:00 PM
Exhibit Hall A

ACTIVE LAYER DETACHMENT SLIDES, KLUANE RANGES, SOUTHWEST YUKON

Paper number: T85-6
Program: Technical Sessions
Time: 9:00 AM – 1:00 PM

Authors

Abstract

Active layer detachment landslides (ALD’s), where the failure plane is the contact between seasonally thawed ground and permafrost, are common in Yukon Territory. Ground disturbance associated with these slides can have a negative effect on water quality, infrastructure and human safety. The close connection between permafrost thaw and ALD’s raises the possibility the frequency and magnitude of these events may be increasing with anthropogenic climate change. This project aims to:

  1. Determine magnitude and frequency changes of ALD’s through historic airphoto analysis
  2. Study the failure mechanisms of a cluster of 25 ALD’s that occurred on or around August 17, 2020, associated with a large precipitation event.

The study area is the central and northern Kluane Ranges of the St. Elias Mountains, southwest Yukon. The area extends from Ä’äy Chù (Slim's River) northwest to the Donjek River and was selected based on an abundance of permafrost related landslides. Fieldwork occurred in July and August of 2020 and included field visits, unmanned aerial vehicle (UAV) based photogrammetry and low-level helicopter flights.

Changes to the frequency and magnitude of ALD’s will be investigated utilizing historic airphotos and satellite imagery. Time intervals of 10-20 years, beginning in 1946, will be used to generate digital elevation models (DEM’s) from airphotos and satellite imagery using Structure-from-Motion photogrammetry techniques. An inventory of ALD’s will be made for each time interval to determine changes in frequency. Changes in magnitude will be assessed by comparing slide area of the each time interval.

The cluster of 25 near-synchronous ALD’s have failure planes marked by the 1250 BC White River Tephra, giving them a distinctive streaky white appearance. Detailed DEM’s generated from satellite imagery indicate a gentle over steep topography. The insulating properties and hydraulic conductivity of the tephra will be investigated to better understand what role the tephra plays in the failure mechanism. Landslide modeling will be preformed to determine a correlation between causative factors and landslide occurrence.

Geological Society of America Abstracts with Programs. Vol. 53, No. 6

doi: 10.1130/abs/2021AM-369887

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