The Barrier

The Barrier
The Barrier is a rock wall formation caused by the damming of lava flows following a volcanic eruption from Clinker Peak on Mt. Price about 12,000 years ago. Lava flowed into the Cheakamus River valley and was stopped by the Cordilleran Ice Sheet, resulting in the formation of a lava dam that we now know as the 250 meter high cliff called the Barrier. The Barrier effectively dammed surface water outflow from the surrounding watershed, and created Garibaldi Lake, Lesser Garibaldi Lake, and Barrier Lake. Water from these lakes seeps from beneath the Barrier via a series of springs into Rubble Creek.

Historical Events and Hazard Overview
Several major landslides and debris flows have occurred on the Barrier since its formation thousands of years ago. These are the main risks associated with the Barrier as rockfall and landslide debris has the potential to block Rubble Creek and cause outburst debris flooding further down on the Cheakamus River. The most recent major landslide on the Barrier in 1855 formed a large boulder field, which gives Rubble Creek its name. In 1981, concerns about additional catastrophic landslides prompted the Provincial government to declare the area immediately below the Barrier unsafe for human habitation, which led to the relocation of residents in the small resort village of Garibaldi to areas away from the hazard zone. Although unlikely to occur, debris flows could affect critical infrastructure near Rubble Creek like Highway 99, and outburst flooding on the Cheakamus could have limited consequences within the District boundary.

Living with the Hazard
The Barrier is considered a physically unmitigable hazard that is instead managed through land use policy, monitoring, and research. Hydrologic floods, earthquakes, and wildfires pose risks that are orders of magnitude higher in terms of likelihood and consequences for Squamish, which is why the District concentrates mitigation efforts and resources on managing these hazards.

Ongoing Research:
The Barrier continues to be studied by a number of academic institutions. Quest University researchers mapped the bathymetry of Garibaldi Lake, Lesser Garibaldi Lake, and Barrier Lake between 2016 and 2018 to better understand the relationship between lake water levels, the lava dam, and Rubble Creek. The volume of water was also more accurately measured in each of these lakes, as well as scanning for drainage points. Researchers from the University of British Columbia have also been conducting terrestrial laser scans of the Barrier since 2017 to determine rockfall rates and detect changes in the surface of the Barrier over time. UBC’s monitoring has shown that although rockfalls occur fairly regularly, the majority of rockfalls are very small: 91% of rockfalls have a volume ≤ 0.1 m3, and only 2% of rockfalls have a volume > 1 m3. Simon Fraser University’s Centre for Natural Hazards Research has also placed monitoring equipment throughout the Sea to Sky region to measure seismic and gravitational shifts that may have an impact on geo-hazards like landslides and rockfalls.

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  • John Stacey Aug 8, 2021, 7:02 AM (2 months ago)

    Was this posted before quest university was funded to do new models that show catastrophic failure for all of Squamish. I mean it’s worth living here still because it’s a great spot and could go in thousands of years. On the other hand it’s been 700 years since our last major earthquake that averages every 500 so we overdue. Go check it out I watched at least 10 yards of material come off this baby over 15 minutes. Does anyone know how much it sheds per year?

    • Communications Aug 17, 2021, 8:43 AM (2 months ago)

      Thanks John.

      The District works closely with the Squamish Lillooet Regional District, the Provincial government, and academic institutions to assess and understand the different geohazard risks in the area, including the Barrier. It’s not known when or if the Barrier will ever suffer a catastrophic collapse. Geologically, it is possible in the next tens of thousands of years that this could occur; however the probability of it happening in our lifetime is extremely low (less than 1 in 10,000, or less than 0.01% likelihood of occurring- similar to an asteroid strike). To put this in context, the 2003 flood in Squamish was considered a much higher likelihood event (1 in 200, or 0.5% chance).

      In theory and keeping in mind the geologic time scale (tens of thousands of years) that these events occur within, a catastrophic collapse of the Barrier could release water from Lesser Garibaldi Lake and Barrier Lake, and could initiate a debris flow capable of blocking the Cheakamus River or running out into Daisy Lake. Some researchers think that catastrophic collapse of the Barrier could also release water from the much larger Garibaldi Lake, although research is inconsistent whether the Barrier will eventually collapse to the point of creating a sudden uncontrolled release of the lake. A much-quoted newspaper article on the Barrier also speculates that collapse of the Barrier could generate a flood wave capable of reaching Vancouver Island; however, the District’s Integrated Flood Hazard Management Plan team confirmed in 2017 that the research cited by this article was taken out of context.

      Research continues to be done on the Barrier. The District has updated this webpage above to provide an overview of the known recent work that is being done by various academic institutions, including a study by UBC on rockfall rates and changes over time to the surface of the Barrier.

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