Speaker:
Jeremy Venditti
Professor – School of Environmental Science, Simon Fraser University
Talk Title: Salmon vs the landslide: The rockslide that blocked the Fraser River
Abstract:
Salmon are iconic animals on the west coast of North America, a critical element of Indigenous culture and an important commercial and recreational fishery. Salmon are born and reared in rivers, migrate to the ocean for 1-3 years, then return to their natal spawning grounds. The Fraser River hosts one of the largest wild salmon runs in the world and is the most productive salmon-bearing watershed in Canada. Successful reproduction requires that salmon pass a gauntlet of fisherman in the ocean and a 375-km long bedrock canyon that is susceptible to blockage by landslides. On November 1st, 2018 the Big Bar Landslide temporarily blocked the Fraser River, initiating the largest and most expensive emergency river restoration projects in the history of Canada. Approximately 8.9×104m3 of rock failed into the Fraser River, creating a 7.5-m high overfall that is similar to a waterfall, but without freefalling water into a plunge pool. Upstream migration success for salmon populations exposed to the highest flows in 2019 was <1%, gradually improving to 80% for populations exposed to lower flows. Blasting the canyon and slide debris in 2020 increased the salmon passage threshold discharge to a level that minimized the potential risk of extirpation for high flow salmon populations in the Northern Fraser Basin. I will report on a research program that used geospatial data, observations of flow dynamics, and radio telemetry to 1) find the next landslide that could block the Fraser River, 2) find other hydraulic barriers to salmon migration, and 3) assess the potential impact of another landslide on salmon abundance and diversity.
Speaker bio:
Jeremy Venditti is a Professor of Environmental Science at Simon Fraser University (SFU). He is the founding director of the School of Environmental Sciences and an Associate Member of the Earth Sciences and Geography Departments. He holds a B.Sc. from the University of Guelph, a M.Sc. from the University of Southern California and a Ph.D. from the University of British Columbia (2003). From 2004-2006 he was a post-doctoral fellow at the University of California at Berkeley. He was a Visiting Associate in 2014 and a Visiting Professor in 2024 at Caltech.
Dr. Venditti has been faculty at SFU since 2006 where he leads the River Dynamics Laboratory. His primary research interests lie in the dynamics of Earth’s largest large river systems, and in particular, the fluid and sediment dynamics of sand-bed, gravel-bed and bedrock rivers. His work current focuses on the dynamics of actively incising bedrock canyons, global sediment export from mountain ranges, and the physics of flooding.
From 2021-2024 he led a team of researchers funded by the British Columbia Salmon Restoration and Innovation Fund (BCSRIF) to examine the impacts of Big Bar Landslide on salmon migration, populations, and genetic selection. His ongoing work focuses on 1) Understanding flow dynamics in bedrock canyons, 2) The distribution of hydraulic barriers to salmon migration in rivers, and 3) The risk posed by landslides and high flow events to salmon abundance and diversity in the Fraser River.
