Spatio-temporal characterization of slope damage: insights from the Ten Mile Slide, British Columbia, Canada

Abstract

The deformation and failure of slopes is associated with the formation of geomorphic features reflecting “external slope damage.” Characterizing the spatial and temporal distribution of slope damage is beneficial to understanding the mechanisms and processes underlying slope instability. To date, characterization of slope damage has predominantly been performed using qualitative approaches. In this paper, a new workflow for the quantitative, spatio-temporal characterization of the external slope damage is described and applied to the investigation of the Ten Mile Slide, an active landslide located in southern British Columbia. Since 2006, monitoring activity at the site has included periodic repeat airborne laser scanning (ALS) surveys, which have allowed the creation of a high-detail, three-dimensional database showing the progressive deformation and retrogression of the slide. External slope damage features are manually mapped in the ALS datasets, and slope damage intensity is then computed and displayed on thematic maps. The proposed workflow introduces important new slope damage measures including External Discrete Slope Damage Feature maps (EDSDF), External Slope Damage Intensity Cell (ESDICe) maps, External Slope Damage Intensity Contour (ESDICo) maps and slope damage intensity spatio-temporal plots. The new spatio-temporal damage measures are used to create damage index tables and track changes in slope damage intensity with time at any point within the slide area. The spatio-temporal analysis shows that the distribution of external slope damage features is not homogeneous across the Ten Mile Slide area. In particular, the spatio-temporal damage methodology outlines higher accumulation slope damage rates along the eastern boundary of the slide area, due to the presence of a stream incision that provides kinematic freedom and allows the lateral deformation of the slide and the formation of tensile cracking. The proposed approach in this thesis allows comprehensive, quantitative, and repeatable damage analysis to be undertaken, providing a robust method for characterizing the geomorphic evolution of slopes from a damage perspective. This research methodology provides engineers and geoscientists with a valuable tool for planning subsequent slope investigation and optimizing new or existing monitoring and early-warning systems.