Behaviour of retrogressive thaw slumps in northern Canada-three-year monitoring results from 18 sites

Eighteen (18) retrogressive thaw slumps (typical landslides in ice-rich permafrost) in northern Canada were monitored for 3 years to investigate the characteristics of their retrogressive behaviour. The head scarp retreat distances and scarp wall heights were measured annually. The first year monitoring results from 13 of the sites were released earlier, which demonstrated a correlation between thaw retrogression rate and scarp wall height. More data were obtained from a subsequent 2 years of monitoring and with five monitoring locations added. The additional data enhanced the initial findings that the retrogression rate increased with the increase of the scarp wall height. An updated correlation between the retrogression rate and scarp wall height is presented in this paper. The effect of slope orientation on thaw slump retrogression was also investigated. The data provided evidence that the occurrence of the retrogressive thaw slumps had no preference over slope orientation. The retrogression rates were also not affected by the slope facing direction.