A scientist is calling for improved monitoring of steep slopes after a major landslide was reported beside the upper Ecstall River, which is a tributary of the Skeena River located near Prince Rupert.
Brian Menounos, a researcher at UNBC and affiliate for the Hakai Institute, said he was first alerted to the Ecstall River landslide by his collaborator, Göran Ekström, a professor at Columbia University.
Ekström has an early warning landslide detection system that identifies areas based on seismic energy or sound waves propagating through the crust. It was through this device that he noticed the landslide that happened beside the Ecstall River on Sept. 1.
A few days later, after the weather cleared, Menounos and his colleagues used satellite imagery and saw there was indeed a large landslide.
Something on the order of about 15 and 25 million cubic meters of material had rapidly descended hundreds of metres down a steep, steep slope,” Menounos said.
An Olympic-sized swimming pool is typically 50 metres long, 25 metres wide and two metres deep. If all of the debris from the landslide was collected, it could fill between 6,000 and 10,000 of these swimming pools.
“This particular landslide encompassed both rock and glacial ice. There was a bit of glacier sitting on top of the steep area that failed. And then that went into a standing body of water which was partially drained as a result of that landslide.”
Menounos was part of a team who used an aircraft about 10 days after the slide to take high-resolution topographic imagery (LiDAR) of the area.
While they are still in the early stages of figuring out exactly what caused it, he said it looks like it could have been triggered by warmer conditions which enhanced melt from the glacier, followed by a late summer rainstorm.
“That amount of water on a steep slope that was potentially unstable was one of the reasons that we felt that it actually occurred.”
Menounos said that higher precipitation is linked to a warmer climate and climate change but the specific rainstorm that led to this slide could still be within natural variability and not pinned to climate change.
Despite this, he still thinks humans and climate change played a role.
At this point, he cannot definitely say it was the straw that broke the camel’s back — it might have been a precipitation event, it might not, but he can point to some of the reasons the metaphorical camel’s back was so arced.
For example, a glacier that had been eroding the foot of the slope and has been retreating for a very long time, long before humans started impacting the environment, he said.
However, the rate it is retreating at has not been seen before and has now been shown by many people to be caused by human-induced climate change. This rapid retreat is destabilizing some of these steep slopes by removing the support of the surrounding ice.
Erosion and glacier retreat have been happening for several million years. In some of these valleys the rapid retreat of these mountain glaciers is suddenly withdrawing ice that may have been occupied in those areas for quite a long time, Menounos said.
“We need to have the ability to, in many cases, monitor these steep slopes in a way that is systemic, that is broad brush, that can alert in some cases, the public, to the potential event that could occur.”
While many landslides occur without any precursor, Menounos said, we can start to identify areas that are more prone to these events.
“In some ways, it’s very similar to earthquakes. We don’t know when the next earthquake might happen but we do know areas or regions or zones that are more hazardous than other regions and so that’s kind of the first stage.”
“The province has been really good about acquiring LiDAR, for example, for low-lying areas for timber supply. But what we haven’t been really good at is collecting LiDAR in our high mountains. And as we are seeing that they are undergoing profound change, we really need to up our game, so to speak.”
Kaitlyn Bailey | Local Journalism Initiative Reporter
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