A Natural Resource Canada research team has just finished a trip into Bute Inlet to investigate the effects of the Nov. 2020 landslide.
Researcher Gwyn Lintern of the Geological Survey of Canada was the lead scientist on the trip. He and his team used advanced echo sounder and laser scanning equipment to determine the amount of sediment that has been deposited by the event. They also collected sediment cores and installed tracking instruments to monitor and future changes.
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“We’ve been in there for the last five years with this international consortium, so we understand the sedimentation of Bute very well. An event like this, wiping out a forest and ending up in the fjord sort of was like the icing on the cake for understanding the sedimentation in there,” Lintern said. “We’ve been looking at the burial of carbon in fjords and natural areas and how well they bury carbon. This changes our numbers significantly, since the whole forest got buried,” he added. “There are these underwater landslides in the area, and we’re trying to figure out what the triggers for those are.”
That international consortium is made of up researchers from the National Oceanography Centre (NOC) in Southampton, U.K., the U.K.’s University of Durham and from the University of Calgary in Alberta. The NOC has applied for an urgency grant to help fund future research projects in the area.
This month, Lintern was part of a six-day expedition to the inlet aboard a Canadian Coast Guard vessel to do a few different kinds of research. The research, which was sanctioned by the Homalco First Nation, whose traditional territory includes Bute Inlet involved a multi-beam echo sounder and laser scanner to scan the bottom and map out the sedimentation that was deposited by the event.
The Canadian Hydrographic Service also took the chance to resurvey the river delta and make changes to navigational charts, and the Coast Guard wanted to investigate existing navigational issues like floating logs and deadheads.
Lintern’s research, however, focused on the sediments in the inlet.
“We were in there in October, and we mapped the seabed, luckily. Then we did a repeat map using a multi-beam sonar that was on board a Canadian Hydrographic Service launch that was carried up there by the icebreaker,” he said. “We just finished the five-year study on understanding that system in and out, so we just had to get up there.”
Lintern and his team have been working on sedimentation research along the coast for years. They have identified quite a few of what they call “events” in the sediment layers, but until now have had no way of identifying exactly what those events are.
“In Bute, we see an event occur about every 25 years. It’s some kind of event or a sand layer. We see a bigger event occur about once every 150 years,” Lintern said. “We kind of speculate about what those events are. So now we actually have an event and we can go out and measure the sediment layers and say ‘OK this is what a sediment layer from a flood looks like.’ That’s important for the science.”
“We have a real event and we can go out and measure it, see what kind of layers it deposits and use that to sort of calibrate the information we get from the layers in other places all along the coast,” he added. “We wanted to see if an event lead to a geological layer immediately? Or is it something that over the next few years will build up layers? These are questions that nobody has answers to. Are these layers deposited over years or over a few days when we see these event layers.”
Apart from the benefit this event has to his field, Lintern is excited about the research bringing together multiple areas of study to understand the event from bottom to top, or what is called studying from ‘“source to sink.”
“Scientists tend to be segregated,” he said. “There’s us in the marine world, then there’s these people who are on the coast, then people elsewhere. This one brings together all of the expertise of the GSC, from the glaciologists, the landslide experts, the tsunami experts, the forestry department … to the ocean. It’s an excellent opportunity to understand an event from the top to the bottom.”
Future expeditions are planned to the area to determine long-term effects of the landslide. The next NRCan expedition will be in March.