Avalanche Mitigation Enters the Future
Drone footage of a large avalanche on Three Pigs Mountain, near Stuart Creek on the Richardson Highway, that occurred in February of 2025. Photo by Kyle Sobek, courtesy of Alaska DOT.
By Allison Sayer
Most of us are familiar with the role of artillery in avalanche risk mitigation. Artillery is fired into avalanche start zones when the runout area is closed to the public, preventing future avalanches that could cause harm. According to Statewide Avalanche and Artillery Program Manager Timothy Glassett, these methods are set to change dramatically over the next two years.
The Alaska Department of Transportation (DOT) currently uses the M119 105 mm Howitzer for avalanche mitigation. According to Glassett, these Howitzers are antiquated to the point where it is hard to find parts. The United States Army still produces shells, but not the cannons that shoot them. Maintenance is difficult.
“The army doesn’t have another viable artillery system for us to use that’s as portable and efficient,” said Glassett. Therefore, the army has told current artillery users, “‘you need to start transitioning away from it.’”
Glassett said the replacement is going to be Remote Avalanche Control (RAC) systems.
RACs are fixed systems built into avalanche start zones that can be triggered remotely to drop an explosive or detonate gases into a tube. “The problem,” said Glassett, “is that each one costs at least $175-200K and is only good for that one location.”
Avalanche 1: Photogrammetry measurements of the crown height of a large avalanche on Three Pigs Mountain. Kyle Sobek estimated this avalanche moved enough snow to bury a football field 300 feet deep. Image by Kyle Sobek, courtesy of Alaska DOT&PF.
DOT plans to install RACs, which are currently only being made by one company, in “high frequency/high risk paths.” A project is “in the works” for these systems to be placed first on the Seward Highway.
Other tools, such as drones, will be needed to supplement RACs. Glassett said DOT is currently “validating the operational use” of drones carrying explosives. This is something that cannot be done lightly; these tools are typically not available to civilians and require extensive permitting.
DOT personnel already use photography drones to enhance their avalanche work. Lead Avalanche Specialist for Thompson Pass Kyle Sobek is often on the ground during mitigation or risk assessment. He frequently sends real time aerial images to supervisors (Valdez Superintendent Robbie Mattson, Tazlina Superintendent Chad Heller, Thompson Pass Foreman Paul Matson), which makes it easier for them to coordinate. Northern Region Information Officer Danielle Tessen shared the imaging is also helpful for her work in communicating with the public.
DOT personnel currently use photography drones to confirm artillery shot locations and to examine avalanche starting zones that are not visible from the highway. Sobek said he can now use a drone to look at the starting zone above 39 Mile on the Richardson Highway in about 20 minutes. Previously, it would have taken him almost a whole day to access the area, if it was safe to do so at all.
Avalanche 2: High resolution map of the avalanche starting zone above 39 Mile on the Richardson Highway. Image courtesy of Alaska DOT&PF.
More frequent monitoring can indicate early when mitigation is needed. Sobek shared there have also been occasions he could cancel avalanche mitigation work because he could see it was not needed. This not only prevents inconvenience to travelers, but also saves considerable staff time.
Avalanche mitigation is extremely staff intensive, often resulting in personnel being pulled from Valdez or the Ernestine Station. This is exacerbated by the staff shortage at Thompson Pass. There are currently two open positions at the Thompson Pass Station.
Collaboration across departments and divisions has been essential for DOT to use new tools effectively. Glassett cited help from Ryan Marlow, Division of Statewide Aviation Unmanned Aerial System Program Coordinator. The DOT&PF Statewide Aviation Remote Sensing Lab has also provided tools and images.
Photogrammetry (photo recording and measurement) tools go beyond just what the eye can see from photographs. Software integrated with photography can make precise measurements, generate detailed microtopography maps, or detect small changes in a landscape feature.
Example of a drone carried photogrammetry tool used to measure an avalanche crown, starting zone, and estimate the volume of snow released. Image courtesy of Alaska DOT.
Overlaying images over one another can help detect how much snow has accumulated on a specific feature, and whether it is dangerously loaded. DOT personnel are also using photogrammetry tools to create detailed maps of avalanches that already have occurred. These maps can help pinpoint the failure points on the mountain.
The more accurately DOT personnel can map snow loading zones and failure points, the more accurately they will be able to place RAC systems in the future.
Of course, avalanche mitigation requires more than just tools. Glassett reflected, “All this tech stuff is useful as long as the person using it knows what to do with it.”
Disclosure: Alaska DOT is a Copper River Record advertiser. This did not affect our coverage.
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