90 Second Column Test

[galibier_numero_un]

Damn! I can barely get my pack/skis off and tools out in 45 seconds, and he's done a quick 'n dirty column test in 90 seconds!

https://youtu.be/_HoGgXneLm4

[simple]

Good stuff

[sf]

So..... Would you guys ski it?
I don't think I would ski with those stability results. Q1 and 14 on the extended seems.....

On the other hand, I've probably skied such conditions a 100 times, when no pits were dug.

[galibier_numero_un]

So..... Would you guys ski it?
I don't think I would ski with those stability results. Q1 and 14 on the extended seems.....

On the other hand, I've probably skied such conditions a 100 times, when no pits were dug.

Maybe on a 25 degree slope with nothing steeper overhead ;-)

And there he is digging in the middle of it. That's what ... 32-33 degrees? A bit too close to 38 for me.

... Thom

[sf]

Yeah, I have no idea about the angle where he's at. It might be below 30, and he might have chosen the spot for pefectly good reasons. Getting a result might be one.

But the results are pretty "orange" in my mind. Interesting to hear what people think

[Bunion 2020]

I have the dubious advantage of knowing that location. It is flatter than it appears and is a common location for a test pit.

It is also a very popular warmup line and does get some skier compaction.

[homemadesalsa]

And recent research has shown that you can get perfectly representative results from digging in the flats, as long as the site is the same aspect and elevation.

Never decide to ski it based solely on 1 pit's results. Are those results congruent with the rest of your information? I have decided, however, NOT to ski something based on getting full propagation on an ECT.

Hi Bunion!

Sent from my HTC6535LRA using TGR Forums mobile app

[John_B]

HMS what's your go to method for cutting out the back/side of a ECT? I've been using a older BD fliklock snow saw attached to a section of a two piece adjustable ski pole. I've always been a little curious as to the effectiveness of the back cut since I am kind of working blind on that one and it feels like the saw can wander a fair amount.

[sf]

I've prefered a cord, but I'm a hack. Requires a partner as well

[Peruvian]

I've prefered a cord, but I'm a hack. Requires a partner as well

Knotted cord seems like a light and relatively easy tool for this.

[homemadesalsa]

HMS what's your go to method for cutting out the back/side of a ECT? I've been using a older BD fliklock snow saw attached to a section of a two piece adjustable ski pole. I've always been a little curious as to the effectiveness of the back cut since I am kind of working blind on that one and it feels like the saw can wander a fair amount.

You can do it with one probe and a cord if you more fully excavate one side and get your hand up there 30cm deep. Hard to not saw on the probe though, unless you get your partner to hold it in place.
I do find that the cord cuts the back of the block more cleanly and completely than the pole-saw, unless you have a crust, in which case you can pre-cut with the pole-saw combo. I've been using the new BD saw which has a bit more lateral stability than other saws. Not a perfect solution.

[auvgeek]

And recent research has shown that you can get perfectly representative results from digging in the flats, as long as the site is the same aspect and elevation.

This is interesting -- I haven't heard that before. Source?

[Not that I would expose myself or others to danger just to dig a pit, but I hadn't seen any real research showing the results are basically the same regardless of slope angle.]

[Foggy_Goggles]

I don't disagree but I would ask what "the flats" are? Any terrain truly flat does not really have an aspect and as such will differ with the respect to characteristics like sun crusts and wind loading.

But yeah, the whole question about what is safe representative location to dig a pit is great.

[auvgeek]

Any terrain truly flat does not really have an aspect and as such will differ with the respect to characteristics like sun crusts and wind loading.

Yeah, I was thinking that myself...

[powhoy]

This is interesting -- I haven't heard that before. Source?

[Not that I would expose myself or others to danger just to dig a pit, but I hadn't seen any real research showing the results are basically the same regardless of slope angle.]

https://avalanche.org/wp-content/upl...T_SlopeAng.pdf

“From a practical perspective, our results suggest that, as long as the snow structure remains reasonably consistent in space, observers can conduct dependable tests in gentler, safer terrain before committing themselves to more exposed areas.”

http://arc.lib.montana.edu/snow-scie...aper_P2.26.pdf

Totally agree that a 5* slope may not give you the most relevant data, as the structure may be quite different, especially if there has been much sun effect, but a 25-30* slope is probably going to have a pretty similar structure to avi terrain while still being a safe place o dig

[I've seen black diamonds!]

https://avalanche.org/wp-content/upl...T_SlopeAng.pdf

“From a practical perspective, our results suggest that, as long as the snow structure remains reasonably consistent in space, observers can conduct dependable tests in gentler, safer terrain before committing themselves to more exposed areas.”

http://arc.lib.montana.edu/snow-scie...aper_P2.26.pdf

Totally agree that a 5* slope may not give you the most relevant data, as the structure may be quite different, especially if there has been much sun effect, but a 25-30* slope is probably going to have a pretty similar structure to avi terrain while still being a safe place o dig

Thanks for that. I read through quickly, curious is this held true only for propagation tests (as seemed intuitive to me), but the second article suggests that isn't the case:

"Recent work shows that such exposure may be unnecessary since the results of extended column tests (ECTs) and propagation saw tests (PSTs) are largely independent of slope angle, allowing for data collection in safer locations. Conversely, some past work shows that compression tests (CTs) are slope angle dependent. In this paper, we test the effect of slope angle on CTs using similar methods as the recent ECT work.... the SnowPilot data demonstrate that the difference between ECTs and CTs is not statistically dependent on slope angle, reinforcing conclusions from our field work. "

It's worth noting that all tests were done on buried surface hoar, which may be touchier than other weak layers. Along those same lines:

"When we tried to access terrain in the low 30 degree range we collapsed the slope and triggered a small avalanche below our study site, attesting to the unstable condition on that sampling day."

So things were sensitive when they conducted the test. I would suggest that the results don't show that slope angle doesn't matter, but that it may matter less than previously believed.

[Foggy_Goggles]

That is a classic example of how I have a hard time integrating academic snow science work into staying safe. I'm sure it trickles down to protocols for the lay person but I find it of little value in the the short term.

"This slope is representative accept when it isn't" "We were performing our science experiment of a buried weak layer so touchy that we couldn't even isolate a column on a test slope". OK

[powhoy]

That is a classic example of how I have a hard time integrating academic snow science work into staying safe. I'm sure it trickles down to protocols for the lay person but I find it of little value in the the short term.

"This slope is representative accept when it isn't" "We were performing our science experiment of a buried weak layer so touchy that we couldn't even isolate a column on a test slope". OK

While I totally agree that it is sometimes hard to find practical take aways in an academic study, I don’t think this is a good example. I think at the very least these studies show that you don’t necessarily have to dig on a slope exactly as steep as the one you want to ride. There may well be situations where slope angle is critical to test results, but it isn’t always. When digging a pit you usually have compromise on something factor in terms of representivity (aspect, elevation, wind-loading, slope angle, etc). These studies have convinced me that digging on slightly lower angled slopes is often a reasonable compromise to make between safety and getting the best possible information. I definitely think about how the snowpack may be different on the steeper slope, but that is no different then when I dig on a slope with a slightly different aspect, or 100’ lower. Sure, it may not be perfectly representative, it it’s better than getting out in the middle of the start zone before having any idea about the snowpack.

[reckless toboggan]

That is a classic example of how I have a hard time integrating academic snow science work into staying safe. I'm sure it trickles down to protocols for the lay person but I find it of little value in the the short term.

"This slope is representative accept when it isn't" "We were performing our science experiment of a buried weak layer so touchy that we couldn't even isolate a column on a test slope". OK

I agree.

I always start digging a pit on the exact slope I'm going to ski, the exact line actually. Then I dig a trench down the entire line I'm going to ski, in order to make sure every slope, aspect, and every other variable in the line is accurately accounted for. Then I'll consider skiing the line. But because there's no line there, as I've dug a trench of snow pit down its entirety, I start at the top again, a few feet over, and start another snow trench. I love alpine touring.

I mean fuck the scientists, what do they know.