Infrastructure Implications from Intensified Permafrost Thaw-Driven Mass Wasting

Presenter:

 

Ashley Rudy – ashley_rudy@gov.nt.ca

 
 
 

Authors:

 
A.C.A. Rudy – Northwest Territories Geological Survey, Yellowknife, NT, Canada
S.V. Kokelj – Northwest Territories Geological Survey, Yellowknife, NT, Canada
J. van der Sluijs – Northwest Territories Centre for Geomatics, NT, Canada
L. Arenson – BGC Engineering, Vancouver, BC, Canada
E. Stephani – University of Alaska, Fairbanks, AK, United States
 

Summary:

The Dempster Highway connects the communities of the Beaufort Delta region, Northwest Territories (NWT) to southern Canada. The highway traverses glaciated terrain comprised of fine-grained ice-rich tills, creating conditions that favour retrogressive thaw slump (RTS) development. Long-term monitoring of an RTS located 800 m upslope of the Dempster Highway (km 28.5) indicated signs of stabilization. Surveys showed minimal volumetric growth between 2002 and 2011 (25 900 m3), and 2015 (33,400 m3). However, in 2017, over 20 000 m3 of slump colluvium was transported up to 300 m downslope, arriving within 200 m of the highway embankment. Evacuation of materials resulted in a fourfold increase in scar volume to 136 500 m3 by 2018 and formation of a second ice-rich headwall, which has coalesced with the smaller upper headwall creating a ground ice exposure >20 m height. Rapid enlargement of this disturbance has increased the potential for large magnitude thaw-driven flows and risk to the Dempster Highway. Field monitoring has informed the establishment of a real-time surveillance system by Department of Infrastructure to manage these risks. This case study highlights the importance of permafrost monitoring programs and strengthening linkages with infrastructure managers to identify and manage risks posed by thawing permafrost.

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