In June of 2019, authorities received reports of the massive Big Bar slide—which actually occurred in November of the previous year—on British Columbia’s Fraser River. The slide, which appeared to be blocking upstream salmon migration in the area known as the Fraser Canyon, kicked off what Simon Fraser University environmental scientist Jeremy Venditti noted was “one of the largest and most expensive emergency river restoration projects in the history of Canada.”
In the wake of this event, in 2021 the Hakai Institute’s geospatial team joined in a major collaborative effort in the Fraser Canyon: to understand the impact of Fraser River landslides on salmon migrations and genetics.
Led by Jeremy Venditti and funded by the BC Salmon Restoration and Innovation Fund, the project—titled Landslide Impact on Flow Dynamics, Fish Migration and Genetics of Fraser River Salmon—set out to answer ten key questions, such as:
What is the frequency and magnitude of landslides that are likely to have blocked salmon migration in the Fraser?
Are there other canyons in the Fraser that are susceptible to future landslides that could cause hydraulic barriers to fish?
How likely is it that a future landslide event in the Fraser Canyon will block the river and impede salmon migration?
Partners included university and government researchers, First Nations, and other experts on the local terrain. Hakai Geospatial’s role was to map the study area in great detail using a variety of techniques.
The geospatial team mobilized the Airborne Coastal Observatory (ACO) to gather LiDAR and other imagery—mapping the area south of Williams Lake to Hope—and also completed the first-ever underwater mapping of the Fraser Canyon, using on-the-water multibeam sonar to map the riverbed. The multibeam component of the project helped to explain river dynamics and where variations in river flow might be challenging to migrating salmon.
Partners
The Hakai Institute was part of a wide array of partners providing expertise and/or funding for this project. Collaborators included Fisheries and Oceans Canada; the British Columbia provincial government; the British Columbia Salmon Restoration and Innovation Fund; researchers in a variety of fields from Simon Fraser University, the University of British Columbia, the University of Victoria, the University of Northern British Columbia, and others; and First Nations representatives from the Nlaka’pamux Nation, High Bar First Nation, and Boothroyd First Nation; the Fraser Basin Council; the Fraser Salmon Management Council; the Upper Fraser Fisheries Conservation Alliance; Rivertec; the Rivershed Society of BC; and Northwest Hydraulic Consultants.
Timeframe
The project started in 2021 and was completed in 2024.
Context
Geospatial data gathered for this collaborative project builds on years of surveying by Hakai Institute technicians using the Airborne Coastal Observatory, as well as on the technical facility our team has in hydroacoustics (multibeam sonar). Through a previous collaboration with researchers at the University of Northern BC, Hakai geospatial specialists had already mapped a significant stretch of the Fraser Canyon in LiDAR prior to the landslide.
Future work in this vein should extend these same efforts into Fraser Basin, such as the Thompson and Chilcotin Rivers. The recent Chilcotin landslide is a good example of where these types of events can occur in tributary rivers and affect Fraser River salmon.
Outcomes
The study identified heightened landslide risk from Yale and Boston Bar, and between Bridge River to White Canyon. Media products produced by Venditti’s team included:
An interactive map showing geospatial data used in the analyses
A “living document” entitled Fraser Canyon Sites of Concern for Future Landslides that shows the sites and their location relative to the traditional territories of the Indigenous Nations along the Fraser Canyon, as well as the potential salmon populations affected
Another interactive map showing which salmon populations could be affected by future landslides
Evidence now shows that historical landslides have likely shaped the biodiversity of Fraser River salmon. After surveys and analysis, the team discovered that there have been 270 significant landslide events in the Fraser Canyon since the retreat of glaciers 12,000 years ago, and they also identified 13 future “sites of concern” where future landslides could block the path of migrating salmon.
Along with identifying historical landslide events and future sites of concern, riverbed mapping using multi-beam sonar also helped researchers identify hydraulic barriers to salmon migration and predict their passability relative to fish size and discharge rates.
As the final report notes, these observations “provide important information for salmon conservation and can be used to better understand salmon migration which in turn helps to inform future mitigation efforts to improve salmon survival rates.”
