Towards quantifying relative activity of re-activated landslides based on high resolution digital elevation model (HRDEM)

Across the Western Canadian Sedimentary Basin (WCSB) post-glacial watercourses have incised deeply into thick glacial sediments and gently sloping Cretaceous-aged bedrock. Since deglaciation, over 12,000 years ago, large landslides have developed in the oversteepened drainage channels and formed the modern day river valley walls. The rate of movement and activity of these valley walls depends on many factors. In some cases, modern river levels are much lower than the water level that led to the original instability and therefore the landslide features have been abandoned and allowed to reach a long term stable slope angle. These features are typically relatively flat, have gently undulating topography and uniform overall slope angles. At the other end of the spectrum historic landslides that continue to be altered by erosion or anthropogenic disturbance typically have bi-modal slopes that are relatively steep and have irregular surface texture. On-ground observations of active slopes most often include open cracks and distressed vegetation, indicative of ongoing movement. Expert judgement based on field observations is typically used to discern between the relative rates of movement in lieu of actual monitoring data. This study aims to use surface texture derived from HRDEM's to map relative levels of roughness for re-activated landslides in northwestern Alberta and investigates the correlation between relate roughness and relative levels of landslide activity as a means for commenting on landslide activity. The Alberta Geological Survey is currently utlizing bare earth LIDAR (light detection and ranging) HRDEM's of two sites, Little Smoky River and Peace River, to assess the relative levels of landslide activity using derivatives of surface roughness. Details of the methodology and prelminary results will be presented.; Figure 1. Preliminary results of spatial analysis of surface roughness at the Town of Peace River based on a 3 m resolution LIDAR HRDEM.