Water Stewardship Information Sources
| Citation | BC Forest Practices Board. 2009. Landslide occurrence following major rain storms on Vancouver Island. BC Forest Practices Board. FPB/SIR/27. |
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| Organization | BC Forest Practices Board |
| URL | https://www.bcfpb.ca/sites/default/files/reports/SIR27%20-%20Landslides%20Updated_WEB.pdf |
| Abstract/Description or Keywords | In November 2006, two large rainfall storm events, occurring two weeks apart, caused major damage to roads, bridges, forests and streams across southern Vancouver Island. These storm events delivered extremely high rainfall and associated high winds, causing hundreds of landslides on Vancouver Island with many occurring in the Bamfield‐Port Alberni area (see map on page 2). In this investigation, the Board set out to analyze the landslide activity that occurred in the two years prior and the year following these two large rainfall storm events. Digital analysis of satellite imagery was used to characterize landslides before and after these large rainfall storm events with respect to their age, years since harvesting of any associated cutblocks and the possible causes of the landslides. Two helicopter overviews were used to confirm the practicality and accuracy of the satellite imagery interpretation. No ground work was conducted. The results of this investigation indicate that following these large rainfall storm events: • The number of landslides increased from 14 slides in the two‐year period prior to the storm events to 107 in the year following the storm events. o There were 12 landslides associated with cutblocks and roads in the two‐year period prior to the storm events, and 95 in the year following the storm events. o The number of landslides on unharvested forest land increased from 2 slides in the two years prior to the storm events to 12 slides in the year following the storm events. • The total area impacted by landslides increased from 8.5 hectares for the two years prior to the storm events to 94.8 hectares after the storm events. • The landslide activity appeared to be clustered in specific areas, rather than spread uniformly across the study area. The number of slides noted in the study area increased dramatically after the large rainfall storm events. The Board suggests that forest managers and practitioners consider the possibility that large rainfall storm events may occur more frequently in the future. Forest managers and practitioners should recognize this potential for increased slide activity when planning future roads and cutblocks in coastal areas of BC. |
| Information Type | report |
| Regional Watershed | Vancouver Island South |
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| Project status | complete |
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