Description and Quantification of Debris Tongue Movement in a Retrogressive Thaw Slump Using Aerial and Terrestrial Photogrammetry

Retrogressive thaw slumps can modify large areas of the landscape and pose a significant threat to linear infrastructure in the Arctic. There is little published information on how retrogressive thaw slump debris tongues develop. This thesis demonstrates a novel technique for combining information acquired from near-monthly structure-from-motion surveys and hourly frequency photogrammetry to reconstruct the development of a retrogressive thaw slump over one thaw season. The study was conducted during the 2019 thaw season at Slump CRB, a retrogressive thaw slump located along the Dempster Highway in the Northwest Territories. It was found that material deposited in previous yeas does not move or change and the new debris tongue material flows over the previous deposits following the path of least resistance. In addition, two debris tongue development stages are outlined to describe the spatial and temporal variability of debris tongue movement and deposition in the early and late thaw season.