| Summary: | Slope failures on transportation routes can kill or injure motorists, derail trains, damage
vehicles, roads and railways, delay traffic, and incur expense to transportation authorities. In
southwestern British Columbia, Highways 1 and 99, the British Columbia Railway, the Canadian
National Railway, and the Canadian Pacific Railway all traverse mountainous terrain, and as a
result are susceptible to a variety of slope hazards.
By quantitatively estimating risk at various areas along a transportation route, high-risk
areas can be identified, risks can be compared with values accepted by society, remedial programs
can be more effectively designed, and their success can be monitored.
A database of 3287 slope failure records was compiled for the five routes mentioned
above. Of these, 1764 records include volume estimates. The effects of data censoring were
reduced by examining spatial and temporal patterns in landslide reporting for failures of different
magnitudes on various sections of each route.
Magnitude-cumulative frequency relationships were plotted for both rock falls and debris
flows on each route. The rock fall relationships each display a power-law distribution for events
greater than 1 m³, and are very similar in form over several orders of magnitude. Geological
conditions along the routes influence the slope of the magnitude-cumulative frequency slopes.
Risk of death due to slope failure on several route segments was calculated using the
magnitude-frequency relationships. The estimates of annual probability of death due to rock fall
range from 0.008 to 0.10, and are below the upper limits of several risk acceptability criteria.
Debris flow risk estimates are less reliable, due to the limited data set. The greatest contribution to
risk to life is generally from intermediate rock falls in the Fraser Canyon (1 to 10 m³), and larger
rock falls in Howe Sound and the Fraser Lowland (100 to 1000 m³). === Science, Faculty of === Earth, Ocean and Atmospheric Sciences, Department of === Graduate
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