Skis as “Anchors” in Avalanches

[Samski360]

I have often heard it said that skis remaining attached to your feet can contribute to a deeper burial in an avalanche. This is often stated while decrying the perils of leashes or expressing the importance of a breakable leash. After a fair amount of internet searching, I can find any studies that actually support that truism.

Is anyone aware of a study or an explanation from an actual expert that supports this “common knowledge”? Similarly, are there any studies that compare burial depths of skiers with releasable bindings vs snowboarders with non releasable bindings?

Before anyone gets too keyboard happy, I’ll say that opinions (unless you’re an actual expert, and don’t just play one on TGR) and anecdotes are not what I’m looking for. The specific circumstances of a singular avalanche burial are too complex to isolate ski attachment as a cause of burial depth.

[Bunion 2020]

Not an expert but I play one on TGR and there was a 33 year stint doing avalanche control in my past.

If you trigger an avalanche you want your skis/snowboard on your feet until you become entrained in the flowing snow, up to that point escape may be possible.

Once you are a part of the granular flow you need to get rid of the skis/board.

[fantastic_damage]

Enough of an anchoring effect with snowboards that there has been money and testing sunk into R&D for quick release systems for snowboard bindings via mini explosives, I dont think these ever made it to production though:
https://youtu.be/40VmKiehAG0

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[skifishbum]

i aint an expert at anything
i do tie off or remove the anchor on the boat and raft and usually remove my strap/leash on the sup when runnin white water for a good reason though

[snapt]

I got slid on while cat skiing some 10 years ago, once I was in the flow I was able to kick one ski off with the other but never able to get the second ski off nor did it release. I distinctly remember being on my right side trying to swim to stay on top, my right leg that held the ski kept getting sucked under, each time this would pivot me upright and then sink me lower into the flow.

[Bunion 2020]

https://utahavalanchecenter.org/blog/55873

Don't Use Pole Straps
Mark Staples
Director, Forest Service Utah Avalanche Center
A standard practice that often gets lost in avalanche education is to not wear wrist straps on ski poles when riding in avalanche terrain. It's not an intentional omission, but there is just so much to learn and only so much students can absorb in a course.
The reason not to wear pole straps is that if you're caught in an avalanche, the snow will pull on your poles and pull your arms away from your body. They can also drag you deeper into the debris. Skis or snowboards will do the same thing. They are almost like a boat anchor. You want to be able to let go of your poles and have your skis come off your feet if you are ever caught in an avalanche.
So, one great option is to remove the wrist straps from your poles permanently. Get used to holding your poles without straps. Some poles have detachable straps that can pop off when pulled hard enough. Regardless of whether you keep your pole straps or not, don't wear them when you are in avalanche terrain.

The specific circumstances of an avalanche burial are too complex to isolate ski attachment as a cause.

BTW the info is out there if you bother to search.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3080528/

Here is something you might like to know.

In the Canadian sample, trauma accounted for more than half of the deaths among people extricated in the first 10 minutes (Figure 1), which highlights the strong influence of trauma on the early phases of the survival curve. The probability of survival at the end of the first 10 minutes was 77% in the overall survival curve for Canada, as compared with 86% in the asphyxia-only survival curve (Figure 1), which highlights the impaired survival phase. However, this presentation reflects only the magnitude of trauma on avalanche survival among completely buried people. In a recent study of avalanche-related deaths in Canada, 33% of all nonsurvivors had major trauma, and only half of the trauma-related deaths involved people who had been completely buried.11 In addition, 44% of those who had a trauma-related death had severe trauma (injury severity score12,13 ≥ 50), which likely resulted in death shortly after burial regardless of extrication time. The study also showed that two-thirds of the trauma-related deaths involved collisions with trees.

[Core Shot]

If Shane’s binders had released properly, he would have survived. RIP

[m2711c]

know your din.

[Samski360]

https://utahavalanchecenter.org/blog/55873





BTW the info is out there if you bother to search.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3080528/

Here is something you might like to know.

Thanks. I read that article before I posted. That was some really valuable info, but didn’t get at the question I’m trying to figure out.

Anyone reading this post should check out that article though.

[Samski360]

Not an expert but I play one on TGR and there was a 33 year stint doing avalanche control in my past.

If you trigger an avalanche you want your skis/snowboard on your feet until you become entrained in the flowing snow, up to that point escape may be possible.

Once you are a part of the granular flow you need to get rid of the skis/board.

This is a really good graphic of distinguishing phases of an avalanche. Thanks.

I am still curious if there is data that looks at the relationship between ski detachment and burial depth. There is a strong correlation between burial depth and survival (excluding trauma), which is why the ski attachment question seems relevant to me.

I know anecdotally people describe skis pulling them down. How do the physics of that phenomenon work?

Relatedly, does that mean that skis with releasable bindings are objectively safer than a snowboard in terms of probable burial depth in a slide?

[John_B]

IANAAE(I am not an avalanche expert) nor do I understand particle movement modeling but I would guess that lower/deeper layers in an avalanche move more slowly due to friction with the bed surface. Having skis attached to your feet gives more surface area for that slower snow to grab onto and to slow your body down causing the faster near surface snow to overtop and bury you.

Take that for what little it's worth.

[Samski360]

IANAAE(I am not an avalanche expert) nor do I understand particle movement modeling but I would guess that lower/deeper layers in an avalanche move more slowly due to friction with the bed surface. Having skis attached to your feet gives more surface area for that slower snow to grab onto and to slow your body down causing the faster near surface snow to overtop and bury you.

Take that for what little it's worth.

That is an interesting theory and directly addresses the question I'm trying to figure out. Let's assume the skier is stuck on their side with skis perpendicular to the fall line. The primary surface area of the ski (top sheet) would be oriented so the snow from the slide would be pushing the skis in the direction of the slide, like a sail. It would make sense that if the snow sliding over the bed surface moved *faster* than top layers, the skis would pull a victim down, because the top of the ski would be getting pulled into the current of the lower, faster moving snow, and the victim would get vectored underneath the slower moving upper layers.

However, if, as you theorize, the lower layer moves slower than upper layers due to friction, it seems that skis on would be a benefit because the primary surface area of the ski (the bases) would be pushing agains the slower moving lower layer, it would keep you higher in the debris rather than punch through to the lower level.

Your post makes me wonder if there is something that occurs at a granular level where a ski causes snow passing around it to "backfill" the space on the opposite side of the ski (kind of like a hydraulic in a river), and that pushes the ski down. In other words, the snow passes around the base and edges of a ski, and then back fills over top sheet of the ski. That backfilling could apply additional force on the top of the ski. This would require the victim to be moving through the snow faster than the general speed of the avalanche debris. If the lower layer of snow were moving slower than upper layers, the upper layer could push the victim (and their skis) through that lower layer faster than the general velocity of the lower layer, producing the "backfill" phenomenon.

This type of theorizing is fun, but I'm still curious if there is data to support the idea. It's interesting that the UAC post described above does not explain why poles (or skis) act as anchors not cite any data (internal or otherwise) to support the assertion.

[CHAIR_97]

Skis are ur friend while you are on ur feet or have a chance to get back on ur feet. After that they are a detriment

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[MTT]

Someone who posts here got caught in an avalanche last year. Toe was on lock so ski stayed on. Messed up his knee. Decscribed being pulled down by the ski.

I believe him.

[Samski360]

Part of my interest in this subject is academic, part is real world application. I was caught in a slide last year. I don’t want to go into details here, but it’s caused me to question everything I thought I knew about snow safety. Part of the reason my bad situation didn’t turn catastrophic was that my skis stayed on and I was able to escape the slide after being carried about 150 ft.

If the common wisdom was “there are too many variables to say skis on or off in a slide is better and it depends on particular circumstances” I’d accept that as the complexity of backcountry skiing. But the “skis as anchors” thing is repeated so often, we accept it to be true. But I have not been able to find an explanation or study that supports the truism. At best we have anecdotes, which can be useful, but have limited reliability or broad application. If I eventually answer this question, I’ll follow up here.

[MTT]

It’s looks like you like to type a lot more than ski

Your tiresome and appear to be wasting peoples valuable time

[Bunion 2020]

but it’s caused me to question everything I thought I knew about snow safety.

That is a huge leap forward.

[MagnificentUnicorn]

Part of my interest in this subject is academic, part is real world application. I was caught in a slide last year. I don’t want to go into details here, but it’s caused me to question everything I thought I knew about snow safety. Part of the reason my bad situation didn’t turn catastrophic was that my skis stayed on and I was able to escape the slide after being carried about 150 ft.

If the common wisdom was “there are too many variables to say skis on or off in a slide is better and it depends on particular circumstances” I’d accept that as the complexity of backcountry skiing. But the “skis as anchors” thing is repeated so often, we accept it to be true. But I have not been able to find an explanation or study that supports the truism. At best we have anecdotes, which can be useful, but have limited reliability or broad application. If I eventually answer this question, I’ll follow up here.

I think it’s simple physics. Skis have more surface area that help you float in snow when you start on top and apply pressure. In an avalanche that same surface area is being affected by pressure on the top sheet instead of the base by snow moving downhill. It’s basically the opposite of what normally happens and that increased pressure drives your skis deeper. I’ve experienced this in larger loose snow slides skiing inbounds on storm days.


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[Samski360]

I think it’s simple physics. Skis have more surface area that help you float in snow when you start on top and apply pressure. In an avalanche that same surface area is being affected by pressure on the top sheet instead of the base by snow moving downhill. It’s basically the opposite of what normally happens and that increased pressure drives your skis deeper. I’ve experienced this in larger loose snow slides skiing inbounds on storm days.


Sent from my iPhone using TGR Forums

I think this is a reasonable hypothesis. But, avalanches are turbulent, so the snow doesn’t necessarily move in a single mass or apply pressure in a single direction. My main point/concern is “skis attached = bad” is a widely stated “fact” for which there doesn’t seem to have been much study. It seems additional evidence is needed to support the statement “skis attached to a victim’s feet in a slide contribute to deeper burial”

Like I said, if I can find any reliable information on this subject. I’ll report back.

[Samski360]

It’s looks like you like to type a lot more than ski

Your tiresome and appear to be wasting peoples valuable time

Who let you out of the padded room?

[cat in january]

You seem to want to die on this hill. What I think has unfortunately been shown to be “bad” with skis attached during an avalanche you are much more likely to suffer leg trauma and this is bad.

[total_immortal]

I also think skis have a lot of surface area and very low volume. So thinking along the lines of an airbag pack, which work because they increase the volume to surface area ratio, i would think they would be more likely to get pulled under as you try and "push" yourself up to try and get out of the slide.

[Samski360]

You seem to want to die on this hill. What I think has unfortunately been shown to be “bad” with skis attached during an avalanche you are much more likely to suffer leg trauma and this is bad.

My narrow question is the relationship (if any) between ski attachment and burial depth. This is relevant to me because historically I skied with leashes and also because I tour with a lot of splitboarders. I’m not arguing a point; just questioning something that appears to be common knowledge, but for which I can’t find supportive evidence other than anecdotes.

Trauma is a separate risk that is also important, but not what I’m trying to figure out. There is a lot of good easily findable information on the relationship between binding release and trauma.

Managing risk is, in part, a process of identifying risks and registering them based on probability and consequence. Often mitigating once risk increases the probability of another. Understanding risks and consequences and their relationships to other risks can help improve decision making.

Apparently despite the vast amount of experience and education in this forum, this is not the place to discuss these types of questions. So I’ll head back to tech talk to learn more about “which red playful charger from Moment or ON3P should I buy?” And we can let this thread die a peaceful death.

[cat in january]

Hopefully you have added a weak link to your leashes. The answer that it is best to become separated from your skis once you are entrained in an avalanche seems quite clear cut. You are looking for an answer to a question that does not lend itself to scientific testing. So you are left with speculation which has been given to you.

[Bunion 2020]

Hopefully you have added a weak link to your leashes. The answer that it is best to become separated from your skis once you are entrained in an avalanche seems quite clear cut. You are looking for an answer to a question that does not lend itself to scientific testing. So you are left with speculation which has been given to you.

I will add that this like so many topics related to snow safety will rarely if ever have a clear cut answer because "getting caught in a slide" isn't as simple as that descriptor would make it seem. It all comes down to, "it depends".

I was caught ski cutting new snow soft slabs after running out of hand charges while on route, I lost the rochambeau with my partner, made the cut, the slope released and entrained me and my fucking skis pulled me under until I was able to ditch them. I did learn that you cannot swim when you have skis on your feet.

I was caught searching for an un-exploded hand charge on a 4F hard slab 2-3' deep and after being carried about 250 vertical I was able to ski off the still mostly solid hard slab, it was just starting to break up.

I was caught ski cutting a new snow soft slab that stepped down into a 1F layer about 3' deep and back above me. I was able to work my way to one side but accelerated to about 70 mph when one and then the other ski were ripped off my boot soles. I was glad to be rid of them.

In each one of those instances there was no clear answer.