Navigating Hidden Danger: Record Snowfall Leads to Tree Well Fatalities

14 March 2024


Sarah Spelsberg MD, FAWM, FEWM & Grace Mensink

Sarah is an Emergency Medicine Physician with a passion for wilderness emergency medicine and orthopedics. She holds a Bachelor of Science from the University of Wisconsin-Madison, a Masters in Physician Assistant from Barry University and completed her Doctor of Medicine at Saint James School of Medicine in Saint Vincent.

When winter blankets the mountains with deep snow, skiers and snowboarders flock to the slopes in search of the perfect run. Amidst the exhilaration of fresh powder and the stunning beauty of a snowy landscape, there lurks a lesser-known but deadly hazard: tree wells. These natural traps are formed around the bases of trees when low-hanging branches prevent snow from compacting near the trunk, creating a void of loose, deep snow that can engulf a person.


The Statistics: A Look at the Numbers

There are an average of 42 fatalities per year at U.S. Ski Resorts. Most of these are from trauma either due to collision with trees or direct contact with the ground. Paul Baugher, the former head of Washington State’s Crystal Mountain Resort Ski Patrol for over 30 years, is the global expert in a skiing death called Snow Immersion Suffocation (SIS). Since 2001, Baugher has been logging every publicised case of SIS at U.S. Ski Resorts. In the United States, tree well incidents claim an average of 4-5 lives per year at ski resorts, prompting a closer examination of the risks and safety measures needed to prevent such tragedies. Considering the millions of skier and snowboarder visits each year, the likelihood of such an incident is low, but the consequences can be severe.


Understanding Tree Wells and Snow Immersion Suffocation

Tree well fatalities occur through a phenomenon known as Snow Immersion Suffocation (SIS). When a skier or snowboarder falls into a tree well, the loose snow can collapse around them, making it extremely difficult to escape without assistance. The risk is compounded when the individual falls headfirst, which can happen if they lose control or collide with the tree at speed. The deep snow can pack around the victim, creating a suffocating trap that limits their ability to breathe and move.


Risk Factors and Contributing Conditions

Several factors increase the risk of a tree well incident. Heavy snowfall, particularly the kind that blankets the Western U.S. mountains, is a significant contributor. Dense forests with coniferous trees are more likely to have deep tree wells. Additionally, off-piste and backcountry areas, with their untouched powder and natural terrain, are more hazardous than groomed runs where tree wells are less prevalent.

Per Adrienne Saia Isaac, Director of Marketing and Communications for the National Ski Areas Association, “The risk of tree well and deep snow immersion incidents increases with big powder days, and we saw some record-breaking snowfall in the Rocky Mountain and Pacific regions in the last season that elevated that risk. And as folks chase powder or visit new ski areas with multi-mountain passes, they can encounter different risks than maybe they’re used to at their home ski area. So resorts and associations like Ski California ramp up the education, especially when significant snowfall is in the forecast, hoping to reach as many people as possible. Ultimately, the goal is to let folks know about the risks of tree wells and deep snow immersion, and to let them know the best practices to enjoy off-piste skiing and riding that mitigate the risk.”


Skiers vs. Snowboarders: Who’s at Greater Risk?

Both skiers and snowboarders are vulnerable to tree wells, but the nature of snowboarding, with both feet attached to a single board, can make it more challenging for snowboarders to free themselves if they fall into a well. Skiers may have a slight advantage due to the ability to use their poles to aid in rescue or to create space around their face for breathing. However, both groups must be aware of the danger and take appropriate precautions.


Prevention and Safety Measures

The key to reducing tree well fatalities is education and prevention. Skiers and snowboarders should be informed about the presence and risks of tree wells, particularly in areas known for deep snowfalls. Ski resorts can play a crucial role by providing information on SIS and tree well safety through signage, pamphlets, and safety courses.

One of the most critical safety tips is to never ski or snowboard alone in areas with potential tree well hazards. Always use the buddy system and keep your partner in sight. If you plan to venture into the backcountry or off-piste areas, carry appropriate avalanche safety equipment, including a transceiver, shovel, and probe, and know how to use them.

In the unfortunate event of a tree well accident, time is of the essence. Immediate action by companions can make the difference between life and death. Skiers and snowboarders should learn and practice rescue techniques, including how to safely extract someone from a tree well.


Resorts’ Role in Enhancing Safety

Ski resorts bear some responsibility to mitigate the risks associated with tree wells. This includes conducting regular safety patrols, marking known tree well areas, and closing off particularly dangerous sections of the forest during high-risk conditions. Resorts can also offer educational programs to raise awareness and teach effective rescue strategies.


The Community Response

The winter sports community has taken steps to address tree well safety, with organisations such as the NSAA and local ski patrols advocating for increased awareness. Online resources, such as, provide valuable information on how to identify and avoid tree wells, as well as what to do if an immersion occurs.


The Future of Tree Well Safety

As technology advances, there may be new ways to enhance safety for winter sports enthusiasts. Innovations in gear design, location tracking devices, and improved rescue equipment could all play a role in reducing the number of tree well fatalities. Moreover, continued research into the dynamics of tree wells and SIS may lead to better prevention strategies and rescue techniques.


Tree well fatalities among skiers and snowboarders represent a serious but often overlooked danger on the slopes. By promoting education, enhancing resort safety measures, and fostering community awareness, we can work towards minimising the risk of these tragic incidents. It is the collective responsibility of the winter sports community.


In the meantime, our hearts go out to the family, friends, and community at large of the adventurer who have lost their lives this year.

Please note: part of the blog post was also published by the same authors in WMS breaking news. World Extreme Medicine was given permission by the original authors to publish this post.

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