Riding the Edge in the Fraser Canyon

Nick Viner is a hydrographer—someone who maps the physical features of bodies of water, whether seafloor, lake bottom, or riverbed. Trained in marine geomatics, Viner worked on bathymetry surveys in the Gulf of Mexico before starting at the Hakai Institute in 2018.

Since then he’s mapped the northwest coast of Calvert Island, British Columbia, and performed aerial surveys with the Hakai Institute’s Airborne Coastal Observatory (ACO) as part of the institute’s geospatial team. In 2021, Viner stepped up as the chief hydrographer for a major multidisciplinary effort: mapping the underwater contours of the Fraser Canyon in British Columbia’s Fraser River.

A mecca for river rafting and the site of the Hell’s Gate Airtram, the Fraser Canyon is famous for steep cliffs and fast water. The canyon is a 375-kilometer stretch of the Fraser River that lies between Soda Creek and Yale. Despite some earlier attempts, no one had been able to successfully navigate this hazardous stretch of the river while deploying multibeam sonar.

Then came a reason to try again, in the form of a massive landslide. In June of 2019, authorities received reports of the slide, located near Big Bar, and learned that it appeared to be blocking the river to upstream salmon migration. As a 2024 report by geomorphologist and Simon Fraser University (SFU) environmental science professor Jeremy Venditti noted, “The landslide initiated one of the largest and most expensive emergency river restoration projects in the history of Canada.”

A lead researcher with SFU’s River Dynamics Laboratory, which does vessel-based fieldwork on river systems and laboratory analyses of river flow dynamics, Venditti helped steer a multidisciplinary research effort to understand the nature of the event and its impacts on the ecosystem. As part of this effort, Hakai geospatial specialists—led by Derek Heathfield and supported by Will McInnes, among others—mobilized the ACO to gather LiDAR and other imagery of the Fraser Canyon.

Viner’s on-the-water work with multibeam sonar took the analysis deeper, literally. It was a tricky endeavor in a charging and turbulent river.

Ultimately, researchers determined that the slide occurred on November 1, 2018, several months before it was reported, and that it had deposited 84,000 cubic meters of rock in the river. That’s about the same volume as 7,500 cement trucks.

The Big Bar landslide jeopardized salmon populations in the upper Fraser basin, but this landslide is not unique—the chance of future slides in the Fraser Canyon is real, and past landslides have likely shaped current salmon biodiversity. The likelihood and impacts of these events on salmon remain uncertain. To improve our ability to respond to this and future events we undertook an investigation of past, present, and future impacts of landslides on Fraser salmon.

—Jeremy Venditti et al. Final Report: Landslide Impact on Flow Dynamics, Fish Migration and Genetics of Fraser River Salmon

Buoyed by their success in 2021 mapping the Big Bar landslide, the following summer the team expanded its scope to a massive survey project to identify past landslides and future landslide risk zones in the Fraser Canyon. These factors could offer critical insights into the future of the river’s salmon populations.

Gathering and interpreting the data involved dozens of university and government researchers, technicians, First Nations, and other experts, including local “technical water services” company Rivertec that safely guided the researchers in their pontoon boats.

After several weeks of surveys followed by analysis, the team discovered—in large part thanks to Viner’s deft hand with multibeam sonar and the expertise of Rivertec’s guides—that there have been 270 significant landslide events in the Fraser Canyon since the retreat of glaciers 12,000 years ago. They also identified 13 “sites of concern” where future landslides could block the path of migrating salmon.

In an interview with Tula Quarterly, Nick Viner explains a bit about the technology he employed and some of his experiences on the river.

Can you explain multibeam sonar in not-too-technical terms?

Long story short, it uses sound to map the seafloor or riverbed and reveal physical features underwater. It sends out a large swath of sound that travels through the water column, hits the bottom, and then is reflected back to a number of small receivers or listening devices. It’s doing this many, many times per second. Using this basic property of sound in water, it’s able to calculate these positions multiple times per second to generate a 3D model of the seafloor or riverbed.

It’s a somewhat simple concept, but the way it’s executed, and how fast it’s being executed—the sheer number of times it can send and receive the signal—makes it a pretty phenomenal piece of technology.

What made the project particularly challenging and memorable?

There were a lot of things, but one of the most basic is just the element of control. A multibeam sonar unit is a very pricey piece of equipment. And so when you’re using it, you’re always very cognizant of keeping it from getting damaged. You want to know how much water is below you, and the conditions of the water and the seafloor. You want to minimize the risks.

When you’re out on the ocean, you have a lot of control over your location and the water depth. If you need to stop, you can stop; if you need to go, you can go. I’d say 99.9 percent of surveying is in those sorts of environments. But even rivers like the Mississippi, which I’ve surveyed before, don’t compare to what we were doing in the Fraser Canyon.

You mean you were out of control?

There’s a reason no one’s really surveyed this section of the Fraser River before. It’s wild. We were working in constricted canyons with whitewater rapids and flows that are so fast and so high that the amount that you can steer the boat and control it becomes super limited. You have to quickly adjust to that new environment. Everything I knew about planning a survey had to just be thrown out the window and we had to develop new methods on the fly.

Were there any particular moments where you felt you were riding the edge in terms of your equipment or safety?

Typically in the past I had done surveys in depths anywhere from 10 meters to, in the Gulf of Mexico, over 2,500 meters. At Big Bar we were above the slide, and there’s also these big sandbars, and so the depth shallows out really quick. I remember a point where we were coming down the river and the depth below the echo sounder got to something like 20 centimeters. And I was thinking, Oh, we shouldn’t be here. But it’s not like you can just stop and turn around—you have to work with the river. But it never got below 20 centimeters, thankfully.

We all knew the risks, and we had everyone’s blessing to do what we were doing. There was this collective agreement that we could lose this equipment. Everyone was pretty realistic about the task that we were about to perform and how, for lack of a better term, crazy it was.

You mentioned that Rivertec was a big help.

Definitely. They run the boats and they’ve been working on this river for decades. Having them there was a huge, huge help. In most places I have data on depths—I know how deep it is, mostly. But on these surveys I had no real data on depths, and so I had to rely on local knowledge.

That was especially true in Big Bar, where there are these big spires of rock. Some of them stick up above the water and you can see them. But they also exist just below water and if you don’t know the river you don’t really know where they are and they can really do some damage.

I would sit down with Rivertec and try to plan how to get the data we needed. They’d say, “Okay, so we can run in this direction, then we’ll pull the gear up and we’ll rip back up.” There were so many hazards that needed to be worked around, but being on the river with Rivertec was just a phenomenal experience. I can’t really put it into words.

Tula and the Hakai Institute were part of a wide array of partners providing expertise and/or funding for this project. Collaborators included: Fisheries and Oceans Canada (DFO); the British Columbia 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; Rivertec; and Northwest Hydraulic Consultants.

To learn more about remediation of the Big Bar landslide under the auspices of the federal and provincial governments and local First Nations, see this DFO page.