What Are Glide Avalanches and Why Do They Matter?
Avalanches are often sudden, violent events, but glide avalanches behave differently. Instead of releasing instantaneously, the entire snowpack gradually moves downhill over days or weeks before eventually failing. This slow movement makes them unpredictable—some glide cracks never release, while others can trigger massive slides with little warning.
Glide avalanches can grow large enough to threaten infrastructure, damage roads, and force prolonged closures. Teton Pass is a prime example, where recurring glide avalanches frequently shut down the roadway, posing significant safety risks for travelers and disrupting transportation.
Glacier National Park’s Haystack Creek drainage is a prime location to study glide avalanches. This area experiences an annual glide event due to meltwater lubricating the snowpack’s interface with the underlying bedrock. Researchers chose this site not only because of its consistent glide activity but also because it provides relatively safe access for deploying advanced remote sensing technology like terrestrial laser scanning (TLS).
The Role of Laser Scanning in Avalanche Research
To capture the full picture of glide avalanche formation and release, researchers need high-resolution, three-dimensional data—something traditional snowpack observations struggle to provide. Manual snow depth measurements are dangerous and limited in spatial coverage, while satellite or aerial remote sensing often lacks the resolution needed to capture fine-scale snowpack deformation.
Lidar has revolutionized snow science over the past two decades, allowing for precise snow depth measurements. TLS, in particular, has been used in avalanche forecasting since at least the early 2010s. Previous studies have employed TLS to monitor snow depth variations and avalanche starting zones, but this research marks one of the first detailed TLS studies of a glide avalanche event.
The research team used a RIEGL VZ-6000 terrestrial laser scanner, which operates at a 1064 nm wavelength and is known for its long-range capabilities. Positioned along the Going-to-the-Sun Road, they captured three sets of scans:
- Before failure (May 17, 2022) – Capturing the intact snowpack and early-stage glide cracks.
- Shortly after failure (June 3, 2022) – Documenting the avalanche debris and release area.
- Post-season (October 18, 2022) – Providing a snow-free reference for depth comparisons.
By scanning from multiple locations, the team minimized terrain shadowing and ensured complete coverage of the avalanche path. The system’s 0.02° angular resolution resulted in point densities of 11–14 points per square meter, allowing for precise mapping of snowpack changes.
Key Findings from the TLS Scans
By differencing the pre- and post-event TLS scans, the researchers quantified the glide avalanche’s impact with an unprecedented level of detail:
- Release Volume: The avalanche displaced approximately 18,674 cubic meters of snow, with an average starting zone depth of 3.3 meters and a maximum depth of 7.2 meters.
- Snow Redistribution: The scans revealed distinct zones of scouring, where the avalanche removed snow down to the ground, and deposition, where the displaced snow accumulated.
- Terrain Influence: The study confirmed that terrain features, such as rock outcrops and drainage channels, played a crucial role in guiding the avalanche’s path and determining its final runout distance.
The ability to quantify these parameters allows for more accurate avalanche modeling and improved hazard assessments in similar terrain.
Why TLS Outperforms Other Remote Sensing Methods
While other remote sensing techniques like UAV photogrammetry and airborne lidar are valuable, TLS offers unique advantages in avalanche studies:
- Higher Resolution: TLS provides centimeter-scale detail, far surpassing the resolution of aerial lidar and satellite imagery.
- Fixed-Position Monitoring: Unlike UAV-based approaches, TLS allows for repeatable scans from the same location, ensuring precise tracking of snowpack changes over time.
- All-Weather Capability: TLS can operate in overcast or low-visibility conditions, where UAVs and photogrammetry struggle.
TLS does have limitations. It is not easy to get a scanner to a scanner to many locations where avalanches occur. Additionally, it is difficult to cover large areas with TLS. For these reasons, UAV and airborne approaches will likely be necessary if these techniques are applied at a management scale.
The Future of Lidar in Avalanche and Snow Science
The success of this study highlights the growing role of TLS in avalanche hazard assessment. By integrating lidar-derived snowpack models with meteorological and stability data, researchers can refine glide avalanche forecasting and improve safety measures. We will write more about that soon.
If you are interested in more details about this study, visit their publication – MAPPING A GLIDE AVALANCHE WITH TERRESTRIAL LIDAR IN GLACIER NATIONAL PARK, USA.
Images from from Dillon et al. (2023), Proceedings of the International Snow Science Workshop.
