Drynoch Earth Flow Remote Sensing Assessment

The Drynoch Earth Flow is located on the east side of the Thompson River, 8 km south of Spences Bridge, in the interior of British Columbia, Canada. British Columbia Highway 1 (Trans Canada Highway) and the CP Rail (CP) main line cross the earth flow, approximately 50 m upslope of the Thompson River. The earth flow has historically been active and both parties have undertaken mitigation since their installation (1860’s to 1880’s); Movement derived from air photographs prior to 1972 indicate an annual movement rate of 2.5 to 3.0 metres per year.​

Satellite based InSAR and airborne lidar scanning (ALS) were utilized to characterize movements of the Earth Flow. Change detection undertaken using three epochs of airborne lidar data was able to quantify displacements on the most active zones of the earth flow, with total annual displacements up to 4.6 m, while the InSAR data were used to quantify more slow-moving zones on the fringes of the earth flow that were not detectable with the lidar change detection, on the order of 1 to 3 cm per year. The combination of the two technologies allowed for better definition of the spatial extents and rates of deformation that can be integrated into future planning of risk management activities in relation to the highway and railway that are located near the toe of the earth flow.