Evolution of the 2014 Vulcan Creek landslide-dammed lake, Yukon, Canada, using field and remote survey techniques

Abstract

The Vulcan Creek landslide is a 1 to 2 × 106 m3 landslide that occurred in southwest Yukon between 15 August and 9 September 2014. The elevation difference between the landslide headscarp and distal extent of the deposit is 370 m and the runout distance is approximately 1.2 km, which corresponds to a farboschung angle of 17°. The material in the headscarp of the landslide consists of highly fractured and disturbed rock mass, due to the presence of thrust faults near the headscarp and toe of the landslide. Overall, the total volume of the landslide is composed of approximately 50% surficial material (colluvium and till) mobilized from the middle and lower slope sections, and 50% of fractured bedrock from the middle and upper slope sections. No distinct trigger was identified for this landslide; however, contributing factors include the long-term seismicity of the area, 10 °C warmer than normal air temperature in January 2014, and approximately twice the normal rainfall for the month prior to the landslide. Long-term permafrost degradation could have also contributed to the slope instability. The landslide dammed Vulcan Creek, forming a lake with a maximum surface area of ~ 22,000 m2. The evolution of the lake and overflow channel was characterized using both field observations and satellite imagery. The lake area decreased between 2015 and 2017 as the overflow channel became more incised and due to sedimentation within the lake. Incision of the overflow channel on the order of 3 m was observed between June 2015 and June 2016. Four years of observations of changes in the lake area and overflow channel dimensions suggest that while the current configuration the landslide dam is likely stable, the associated hazard to recreational users in the area changes with time as the lake volume varies and the stability of the slope above the lake evolves.