The characterization of drainage related landslides on gentle-over-steep forest terrain in the interior of British Columbia

The Southern Interior of British Columbia is an environment where slope instability is frequently linked to the influence of groundwater recharge through forest road drainage networks. Slope failure commonly occurs below the gentle-over-steep break of slope. To gain an understanding of this environment a detailed field investigation was conducted to characterize a representative population of gentle-over-steep landslides. Slope angles above and below the break-in-slope, the proximity of logging roads to the slope break, surficial material type and thickness, and the shape of the slope at the transition from gentle to steep slopes are identified as important factors that control near surface water flow and should be considered prior to forest development and road construction.;A program of computer-modelling was undertaken to further the understanding of the subsurface water flow regime on gentle-over-steep terrain. Combined finite element groundwater flow and stress deformation models indicate the potential importance of soil liquefaction prior to slope failure, a condition that is believed may occur on gentle-over-steep terrain. (Abstract shortened by UMI.)...