An author who lives in a snowy country explains about tree holes that you should be careful about when skiing or snowboarding

　The 3rd year of Reiwa is about to end with heavy snowfall nationwide, mainly on the Sea of ​​Japan side. What worries me about the short-lived sunny weather is skiing and snowboarding. Especially when the snow is just beginning to fall, it may become impossible to escape by falling into a tree hole or stream.

　In Niigata Prefecture, where the author (note) lives, especially in Echigo Yuzawa (Yuzawa Town), the amount of snow has reached a depth of 130 cm, making it worthy of being called "this is the snow country". The snow that continued to fall from the night of the 24th is about 80 cm in 24 hours, and the weather forecast is for heavy snowfall (which is normal in snow country).

　Heavy snow does not simply refer to 2 m of snow (accumulated snow), but refers to snow that fell about 1 m in one night (snowfall). The reason is that 2 meters of snow can be cleaned up, but 1 meter of continuous snow can be overwhelming.

What is a tree hole?

　There is a hole under the trees in the snow country. This is called a tree hole. During the snowy season, larger ones are seen at the roots of conifers than at the roots of deciduous trees. For more information, please refer to the author's article, "A tree hall with heavy snow and its dangers explained by a resident of the snow country".

　During the winter, from the time the snow begins to fall until the snow melts, it continues to exist, but it is at its most dangerous when the fresh snow begins to fall.

See Figure 1. Two days ago, on December 28th, the children started to build a snowy mountain under the trees on the upper right during the most dangerous time of the fresh snow. There is a freshly made tree hall in the lower left from the center of the photo. The depth is about the height of a child. The guardian wasn't there, so when I tried to tell him to get out of the tree, he didn't leave. I'm glad nothing happened.

About the dangers of tree holes in fresh snow

(1) I don't notice the existence of the tree hole itself

(2) It is extremely difficult to climb up after falling.

(3) Snow piled up on trees falls and fills them

Everything is dangerous because it is fluffy because of the fresh snow. In particular, when there is news of a distress accident with expressions such as going out of the sliding area and hitting a standing tree while skiing or snowboarding, or being unable to escape, many of them are related to depressions, including tree holes. increase.

What happens when you go outside the ski area?

　At the ski resort, the ski area is clearly defined, and if you enter the ski area without permission, "the lift ticket may be taken away". There are even ski resorts that warn. It's such a dangerous act.

Falling into the tree hall

Video 1 is a video of the tree hall outside the ski area. This is a place where relatively out-of-area skiing takes place. It was the first sunny day after the fresh snow piled up, so you can see that there are traces of skiing on the fresh snow.

　The video first shows the footage of the hall taken from the bottom of the slope. After that, I moved up the slope and photographed the entire tree. When viewed from above, the existence of the hole is not noticed at all. I will approach it little by little, but I still do not notice the existence of the hall. After going around the trees, the hall finally came into view.

　From here, I set up an emergency escape method and went down into the tree hall, just like I would enter a dangerous water area. At the bottom of the hole, the snow is about 1 m deep, and the surrounding area is surrounded by crumbly fresh snow. In addition, if you do not set the correct escape method, you will really be in trouble, so please do not easily imitate the video.

Video 1 I went down into the tree hall (photographed by the author, 1 minute 59 seconds)

Falling into a stream

　There is definitely a stream running through the V-shaped terrain in the ski resort. However, when the fresh snow piles up, the creek becomes completely unrecognizable as it is buried in the snow. In addition, since it is a gentle depression overall, it looks like a U-shape rather than a V-shape in such snow-covered areas.

　In the U-shape, even if you get stuck, you will fall into the illusion that you can climb up, but that is not the case. And no matter how shallow the stream, the water temperature is extremely low, and if the water enters through your ski boots, your feet will become sluggish.

　The above few lines are actually an incident that I encountered when I was a ski patrol when I was young. Even with a few patrols, human rescue was impossible. Luckily, the skier was wearing gloves and his fingers were tense. It was my first experience with cold water salvage.

It is almost impossible to escape on your own

It is difficult to escape on your own from a depression like Shinsetsu Tree Hall. The reason is that when you get stuck, you slide on skis and get stuck, but when you escape, you have to remove the skis and boards.

　It is quite difficult to go up a slope with fresh snow in ski boots. The aforementioned skier who fell into the creek was initially unable to climb the fresh snow slope. And even if you can climb, walking in the fresh snow is extremely physical. Please think that it is impossible to return on foot in the fresh snow for the distance you skied.

Video 2 shows walking in fresh snow with a depth of 130 cm while wearing boots. I'm buried in snow up to my crotch, and I'm taking the next step by lifting my toes above my crotch. Did you go about 10m? Tired and down.

Video 2 I tried walking in boots in the fluffy fresh snow (photographed by the author, 1 minute 15 seconds)

　This is also a difficult question as to whether the ski patrol can rescue them. In the first place, patrols can only go as far as they can go on skis. Descending into a treehole or creek means meeting a rescuer.

If you know ring snowshoes, you might say, "Rescue teams will wear them and get close to the scene." But it's an illusion. Snowshoe snowflakes are effective during the season when it is possible to walk on frozen snow (when the surface of the snow freezes and becomes slightly stronger), but they are almost useless in fresh snow.

See video 3. The old-fashioned ring snowshoe is not effective, so it is shown how to change to a modern plastic snowshoe and walk on fresh snow. It's a little better than boots, but you can still see him walking in the snow up to his knees.

Video 3 I tried walking in the fluffy fresh snow with Kanjiki (photo by the author, 1 minute 31 seconds)

To save lives

I can understand why you want to ski or snowboard on soft, fluffy fresh snow. But if you go out of the runway area, you can't do it.

　In the unlikely event that you get stuck in a depression in fresh snow, call 119 on your mobile phone and call a rescue team. Rescue teams in the snow country can get close, but rescue and transportation by ground forces can be extremely difficult depending on the situation. In that case, the air force may carry out a hoist rescue. The procedure is the same as a water rescue operation for a fisherman stranded in rough seas.

Note　Although I am a specialist in water accidents, the processes involved in snow-related accidents and water accidents are quite similar. Combined, I think it has become a new genre construction. For example, the relationship between ice and water, the relationship of suffocation and hypothermia if submerged, and the fact that the brakes do not work are similarities between cars and boats. We will deliver the facts that the residents of the snow country saw with the eyes of science in the field in the article.