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12th January 2023
...Continued from PART 1

If more floods are expected, the question becomes when. In recent years, improved seismometer sensitivity, lidar, and satellite imaging are providing scientists a boost in understanding these events, but predicting a landslide is nearly impossible.

“Predicting where something might happen is the easiest [part],” Geertsema says. “Predicting when it will happen is more difficult.”

Some slides—Elliot Creek and Chamoli included—show a slow creep in the months or years leading up to an event. Others give way without warning, making it hard to provide notice to anyone who might be in harm’s way.

Most of the time, researchers must sift through the debris after the fact like detectives to figure out what happened. But the Elliot Creek disaster occurred in a richly studied area—providing researchers the equivalent of video surveillance of a crime scene.

In recent years, lidar data—a remote sensing technique using lasers that can provide precise 3-D surface mapping—of the Elliot Creek watershed and water samples from Bute Inlet have been collected by a forestry company and the Hakai Institute. Comparing this with similar data collected after the slide, Geertsema and his colleagues had a wealth of information to plug into computer models to map the event’s destructive path from sky to sea.

The researchers’ results show how the landscape changed in incredible detail. In its rush downhill, the flood eroded tens of feet of sediment in some areas and deposited enough to bury a truck in others. Analysis of the water samples showed that upon entering the ocean, the water cooled the inlet depths half a degree Celsius—instantaneously bucking a 70-year trend that has seen 1.3 degrees Celsius warming—and dramatically increased oxygen levels. Even seven weeks after the flood, turbidity levels—which measure how much sediment clouds the water—in the Southgate River were up to 32 times higher at the affected area than they were farther upstream, where the flood didn’t reach.

While the researchers have pieced together the minutiae of what happened, they still don’t know exactly what triggered the initial landslide. The precise cause will likely never be pinpointed, but it’s clear to the researchers that the recent accelerated retreat of the glacier, which had shrunk by some 1.5 miles in the past 50 years, played a crucial role.

With rising global temperatures, those living in the shadows of glaciers will likely see more catastrophes in coming years. But with ongoing monitoring and an increased understanding of glacial lake outburst floods through studies like the one at Elliot Creek, there’s hope future events can be mitigated by improving risk assessments and planning future developments and population centers more mindfully.

“We are in crisis mode,” Blaney says. “We really need to come together to figure this out.”

Mara Johnson-Groh is a freelance science writer and photographer who writes about everything under the sun, and even things beyond it. Her work has been featured in publications such as Science News, Scientific American, NASA, Discover, and more.

Lead image: Runja / Shutterstock


1. Geertsema, M., et al. The 28 November 2020 landslide, tsunami, and outburst flood—a hazard cascade associated with rapid deglaciation at Elliot Creek, British Columbia, Canada. Geophysical Research Letters 49, e2021GL096716 (2022).

2. Shugar, D.H., et al. Rapid worldwide growth of glacial lakes since 1990. Nature Climate Change 10, 939-945 (2020).

3. Maraun, D., et al. A severe landslide event in the Alpine foreland under possible future climate and land-use changes. Nature Communications Earth & Environment 3, 87 (2022).

4. Stuart-Smith, R.F., Roe, G.H.,Li, S., & Allen, M.R. Increased outburst flood hazard from Lake Palcacocha due to human-induced glacier retreat. Nature Geoscience 14, 85-90 (2021).