Landslides are a hazard in northeast British Columbia. Each year, mass wasting events adversely affect:

• oil and gas infrastructure
• road corridors
• other public and private assets

Most landslides in the northeast occur in silt and clay-rich Quaternary-age sediments and Cretaceous-age shales. Understanding the underlying geology and different triggers helps predict where landslides are likely to occur.

Information Available

The Ministry of Energy, Mines and Petroleum Resources contracted BGC Engineering Incorporated to complete a report on terrain hazards in northeast British Columbia. Entitled Stage 1: Review of Terrain Hazard Assessments and Mapping in Northeast British Columbia (PDF 680KB), this report:

• reviews the current state of knowledge of terrain hazards in the region
• compiles existing terrain hazard maps
• includes an inventory of known landslide occurrences
• incorporates discussions with researchers and industry stakeholders
• provides recommendations on future directions for terrain hazard assessment

The area studied in the report is outlined in the map Terrain Stability and Landslide Mapping for Northeast British Columbia (PDF 15MB). Summarized here is mapping conducted to date. This map also includes locations of known landslide events.

Colluvial Aprons – Potentially Unstable Landforms

Colluvial aprons are typically located at the base of slopes in river valleys, but can also occur in higher elevation settings at the base of slopes associated with mesa topography. Where they cross river valley bottoms, oil and gas pipelines are often built through colluvial aprons.

Colluvial aprons are a concern for those involved with the development of oil and gas infrastructure as:

• Aerial photographs and pipeline incident reports indicate down-slope movement in these landforms
• Movement in these features, though usually of lower magnitude, is thought to be frequent or continuous
• There is a lack of data on the nature and timing of movement within these features

Terrain Hazard Research

In an effort to characterize down-slope movement within colluvial aprons, the British Columbia Ministry of Energy, Mines, and Petroleum Resources – in collaboration with the Geological Survey of Canada and the Canada Centre for Remote Sensing – is implementing a pilot monitoring program using radar corner reflectors and interferometric synthetic aperture radar (InSAR). The movement of reflectors installed on colluvial aprons will be determined using reflected beams from RADARSAT. During the summer of 2007, 15 corner reflectors will be installed at two different sites. At the end of the first year of monitoring a report will be published that presents data collected over the year and will comment on the effectiveness of the pilot program.

Research is also being conducted on automating the delineation of setback distances for slopes susceptible to failure. This research is being conducted in a GIS environment for an area where landslide mapping has been conducted and for which there is an existing database of landslide occurrences. The resultant slope hazard polygons will be compared with these data to assess the effectiveness of this method.

References (266KB Word) on terrain stability, terrain hazards and surficial mapping in northeast British Columbia.

For more information, on the Northeast British Columbia Terrain Hazard Program, please contact: