Danger lurks in snow country tree wells

One of the lesser-known hazards of snow country travel is the danger posed by tree wells. Tree wells form around the bases of evergreen trees when overhanging limbs interfere with the natural deposition of falling snow, and the resulting cavities can be deadly.

When a uniform blanket of snow is disrupted by tree limbs, the opening created around the tree trunk can partially fill with loose, unconsolidated snow. Like quicksand, these cavities can swallow a person in an instant. Such an accident can be compounded by snow adhering to overhanging limbs, which will often be dislodged on impact, further burying the victim.

Survival chances for a buried tree-well victim are very poor. Termed Non-Avalanche Related Snow Immersion Deaths (NARSID), suffocation can occur in minutes, especially when a skier or snowboarder enters a tree well head-first.

Unfortunately, such fatalities are not uncommon, and several occur in North America each year. Eleven years ago this month, a Bend snowboarder disappeared on Mt. Bachelor, and, despite an extensive ten-day search, she was not found until weeks later, the victim of suffocation in a tree well.

Five years ago, a Mount Hood snowboarder suffocated in a tree well after just 15 minutes, in spite of the fact that three other persons were on-scene and attempting to extricate him.

Two years ago, British Columbia ski-patrol members were conducting a training exercise when one of the patrol members suffered an unplanned, head-first fall into a tree well; and the training session turned into a very real rescue mission.

Even with multiple experienced and well-trained ski-patrol members immediately on scene, several minutes were necessary to free the victim, who fortunately survived. Typically, victims are completely immobilized in the loose snow, and struggling only compounds the entrapment.

Tree wells are a danger in the backcountry, but incidents can occur anywhere. One Santiam Pass ski patroller tells of an incident when a skier became trapped in a tree well only about 15 feet off a principal groomed ski run.

"He was skiing alone and lucky that someone saw him go into the tree well," the rescuer said. "He was hung upside down by his skis and you couldn't see or hear him."

In this case, a rescuer had to go down inside the tree well with the victim to release the victim's ski bindings, which held him prisoner. With the aid of another ski patroller, the victim was finally pulled to safety.

In another similar incident, a skier plunged headfirst into a tree well, and no one saw the accident. That skier was trapped upside down, completely immobilized and helpless. Fortunately, the victim was able to breathe but would probably have died of exposure had he not been able to reach his cell phone and call for help. As a result, help arrived; and the trapped skier survived.

The snow pack in our local mountains is deep right now, and will probably grow even deeper. New-fallen snow can easily create and obscure potential tree-well traps. The best way to avoid the danger is to steer clear of trees and other topographical features, such as rocks or creeks, where such wells could be present. Ski patrol officials urge caution and warn that skiers and snowboarders in the backcountry should carry shovels and never travel alone.

Another way to avoid tree wells - or at least to reduce the chances of encountering them - is to travel in one of our many burned-over forests. Here, the dead trees have been largely stripped of needles and limbs. As a result, the snow falls in a more uniform fashion that does not lend itself to the formation of tree wells and the resulting unconsolidated loose snow that acts as a trap.

Curiously, as dangerous as tree wells can be, under certain circumstances, the natural snow cavities can also be used for shelter in an emergency. Very deep tree wells, with unconsolidated snow, should never be entered. However, if the snow is firm and the well is not too deep, a tree well can be the nucleus around which to build an emergency shelter.

When used together with a small plastic tarp, skis and tree branches can be utilized to form a roof for a shelter that can be quickly constructed over a tree well. Emergency supplies, and especially space blankets, should always be carried in the backcountry. While it might seem like a nuisance to carry the extra weight, if an unexpected overnight bivouac becomes necessary, such precautions can be the difference between life and death.