A New Protocol to Map Permafrost Geomorphic Features and Advance Thaw-Susceptibility Modelling

Permafrost thaw can destabilize terrain, initiate thermokarst processes that alter landscapes, and create geohazards for communities and infrastructure. A robust, standardized methodology was developed to map indicators of thaw-sensitive permafrost terrain, including mass wasting and periglacial features. The method was applied to a 10-km wide corridor centred on the Dempster and Inuvik-Tuktoyaktuk Highways, which are constructed over a wide range of terrain and permafrost conditions. Here we use random forest models, trained and validated with mass movement and ice-wedge polygon inventories, to develop thaw-susceptibility models for two regions along the corridor, Peel Plateau, and Anderson Plain and Tuktoyaktuk Coastlands. Geomorphological and hydrological variables were used as predictors providing insights into the characteristics constraining the distribution of thaw-sensitive terrain. In the Peel region, mass movements have a higher potential of occurring on concave, moderate to steep slopes (7 to 18°) in fluvially-incised valleys. In uplands of Anderson Plain and Tuktoyaktuk Coastlands, mass movements occur on moderate slopes (5 to 15°) adjacent to incised stream channels, and along lakeshores. The ice-wedge polygon model across the forest tundra transition north of Inuvik highlights the northward increase in polygonal terrain with decreasing ground temperatures.