Two rockfall events sent boulders crashing onto popular B.C. hiking trail

A popular hiking trail in Squamish, B.C., remains closed after officials have now determined two separate rockfall events damaged the park.

B.C. Parks closed the Stawamus Chief main trail on Dec. 27 as a large section of the trail was covered in debris, including rocks and fallen, broken trees.

A spokesperson with B.C.'s Ministry of Environment and Parks said a geohazard assessment was conducted on Jan. 2.

Originally, it was believed that one rockfall event had occurred. However, after the assessment, it was determined that there were two slide events.

The first slide took place on Dec. 26 around 10:30 p.m., and the second slide was on Dec. 29 around 11 p.m.

The assessment found that several large rocks, approximately three to four metres in diameter, came down, crashing into trees and also taking the soil with them onto the trail.

Squamish-based geoscientist Pierre Friele believes a freeze-thaw scenario caused the rockfall due to the fluctuating temperatures on the day.

“It perfectly matches the temperature dropping from above zero to below zero, and then boom, you get the rockfall,” said Friele.

He also added that these types of rockfall events are very challenging to predict and he expects more rocks are likely to fall in the area.

Friele has lived in Squamish since 1990 and has been working the corridor for 30 years.

“There wasn’t really any rockfall reported on the Chief [trail] for many many years,” Friele said. “There was really only one significant event and that was in 1999 and then in 2015 we had a really big one that has left that scar.”

Since 2021 there’s been regular rockfalls he said.

“It's really a new trend on the mountain,” said Friele.

Friele said this could be tied to more people documenting the rockfalls or changes in climate patterns.

“If we're moving into kind of more intense climate patterns, with longer duration and more intense rainfall and more crossing over of this sort of freeze-thaw boundary, then we're going to see more rockfall,” Friele said.

After the rockfalls, he visited the area but said it was difficult to see the start zone of the rockfall. The debris field is near the start of the trail for the first peak, at the bottom of the stairs.

The park remains closed indefinitely, with no timeline determined for clean up.

“Next steps will require rock-scaling prior to cleanup of debris and reopening the trail to ensure no loose rocks remain,” said a spokesperson.

Cleanup will include rock removal, removal of fallen trees, addressing hazardous standing trees, soil removal, and rebuilding damaged infrastructure.