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UBC Theses and Dissertations

Failure behaviour of bedrock and overburden landslides of the Peace River Valley near Fort St. John, British Columbia Van Esch, Kristen Johanna Brearley


A reach of Peace River between Fort St. John and Hudson’s Hope flows in a steepsided valley cut by meltwater and Holocene river flow through Cretaceous shale and sandstone covered by clay‐rich glaciolacustrine deposits. Numerous landslides occur on the banks, initiating in both the bedrock and overburden. Following a recently completed local landslide inventory and the completion of an airborne LiDAR survey, five landslides have been examined in detail: the Attachie Slide, the Moberly River Slide, the Halfway River Slide, the Cache Creek Slide and the Tea Creek Slide. Analysis of the five case studies suggests that most slope movements can be attributed to one of four dominant landslide failure mechanisms: compound rock slides, compound overburden slides, shallow rapid flow slides, and earth flows. Compound slides in bedrock and overburden are morphologically similar. Most have the character of compound slides, exploiting weak horizontal clay layers found at multiple levels in both materials. Typically, a sliding surface develops along a bedding plane presheared to residual friction and connects to a steep main scarp cross cutting the layers of rock and soil. Frequently this mechanism then repeats successively at multiple levels. The Cache Creek Slide and Tea Creek Slide are examples of compound slides in bedrock. The Moberly River Slide and the Attachie Slide are examples of compound slides in overburden. The toes of the slide deposits often assume the character of earth flow tongues which are intermittently removed by river erosion. Shallow rapid flow slides, such as the Halfway River Slide, are also common in the normally consolidated glaciolacustrine silts and clays of Glacial Lake Peace that overlie the study area.

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