T218 Landslide Hazard and Risk Assessments I

Thursday, 29 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

LANDSLIDES THAT HAVE CAUSED FATALITIES IN CANADA SINCE 1771

Paper number: T218-2
Program: Technical Sessions
Time: 1:35 PM – 1:50 PM

Authors

Abstract

A revised compilation of historical landslide events that have caused fatalities revealed that at least 785 people perished in Canada from 1771-2019. British Columbia (BC) experienced the highest number of fatalities at 355 (45%) and Québec, the 2nd highest, at 239 (30%). These fatalities mainly reflect development within the landslide prone mountainous terrain in BC and Alberta (73 fatalities; 9%), and sensitive glaciomarine clay areas in Québec. In Newfoundland and Labrador (NL), rockfall from rugged shores are the main reason for 103 fatalities (13%). Fatalities only occurred in two other provinces and one territory: Ontario, 13 fatalities (2%), and 1 fatality (0.1%) in both New Brunswick and the Northwest Territories. The lack of fatalities in the other provinces and territories re likely related to fewer potentially fatal landslide events and low density of population and development.

The greatest number of landslides and associated fatalities occurred during the 1880s to 1920s, when major infrastructure corridors were developed, but landslide hazards were poorly understood. The most common months for fatal landslide events were September to January. In coastal BC, this reflects the occurrence of debris flows triggered along steep mountainous channels by high intensity rainfall events during the fall and winter months. In the St. Lawrence Lowlands, spring (April, May) and fall (September, October) months are the most common for fatal landslides in sensitive clays.

The worst Canadian landslide disaster occurred in the mountains in 1903 at Frank, Alberta, where 73 people perished from a rock avalanche that buried a mining town. Since the event, no development is allowed downslope. In Québec, 35 historical landslides caused 239 fatalities; 24 of these occurred from landslides in sensitive clays. In 1908, a landslide in sensitive clays along the Liève River across from Notre-Dame-de-la-Salettte generated a displacement wave that caused 34 fatalities. Since 2003, the Québec Ministry of Transportation has developed regional landslide susceptibility maps for most areas to help mitigate landslides in this region.

Since the 1770s, understanding of landslides and their potential triggers has led to several mitigation measures and thus, fewer fatalities per decade.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-354152

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