Timely Avi Danger Reminder - Mt Bogong

Discussion in 'Backcountry' started by Hully, Jul 12, 2017.

  1. Hully

    Hully Dedicated Member

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    Got shown pics and first hand account of a recent significant avalanche in Tombstone Gully on Bogong. The skiers involved were pretty much as experienced as you get in the Australian mountains and if it involved less experienced people, like myself, a likely result may have been fatal. Skier triggered with a 1.8mt avalanche crown and it ran full width of the gully and up a ways either side.
    With more snow forecast in the upcoming days a trip into the backcountry is going to be super attractive....stay safe, play it safe, make it home to ski another day.
     
    #1 Hully, Jul 12, 2017
    Last edited: Jul 12, 2017
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  2. Hully

    Hully Dedicated Member

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  3. The Bluff

    The Bluff Active Member
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    Whoa...makes me feel totally out of my depth!
     
  4. Ralph_Plow

    Ralph_Plow Active Member

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    Ski cutting on a convex loaded slope. The question is why.
     
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  5. Tanuki

    Tanuki Dedicated Member
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    My initial thought as well. Pulled out my avi guide book and it's one of the big red flags...
     
  6. sbm

    sbm Dedicated Member
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    WOW that is a big one. Biggest skier triggered avi ever recorded in Aus? The one in Alan Andrew's book sounded like a similar size.

    Of note - no weak layer, facets, hoar frost or any of the usual suspects - just a huge wind slab sliding on the new snow/old crust interface (which seems to be the mechanism for most dry slab avalanches in Aus, it would be extremely uncommon for us to get hoar frost surviving the pre-frontal wind and rain, or for it to get cold enough for a strong temperature gradient for facets)

    Because most of the time in Aus wind loaded slopes are the only slopes with enough cover to ski on and consistent soft snow. Lets be blunt our snowpack is pathetic. We unconsciously train ourselves to seek out wind loaded gullies as they have the best chances of full cover and soft snow when it's bit lean.

    IIRC Hakuba Damien noted this when he skied Bogong, and put a note in on his blog for northern hemisphere readers, clarifying that yes, looking for windblown drifts would be seen as suicidal in the backcountry anywhere else, but is common for canny Australia skiers.
     
  7. sbm

    sbm Dedicated Member
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    My uneducated guess is the reason we don't see more skier-triggered avalanches in Aus, is that the main mechanism for our avalanches (windslab sliding on an old snow interface) stabilises relatively quickly once the loading has stopped (in a matter of hours if I recall correctly). So there is a small window for all the elements to come together to cause an avalanche, and that involves skiing steep slopes in bad weather.

    We don't get large amounts of snow, or have large areas of snowpack for snow to be transported from, once the front has passed and western faces are stripped the danger mostly passes, unless you really shock the windslabs with eg a collapsing cornice.

    So for you to be travelling in considerable or high risk in the Australian high country, firstly you need a freeze on the old snow layer (damp or sun-melted snow will stick), secondly you need to be on a properly steep double-black-diamond slope (very steep by our standards), and then you need to be either 1) travelling in the middle of a blizzard while new snow loading is occuring, like the guys on Bogong a few years ago or 2) travelling right after a big howler has sprung up, blowing different direction to the way the last front was blowing, which will shift snow from one aspect to another and start loading the slabs again for a few hours.
     
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  8. telecrag

    telecrag Part of the Furniture
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    Same reason you use a log to lever a rock off a cliff?

    I have done the same thing on a much smaller scale, kind of thought it might hold, but had my doubts, so cut it. Surely most here have at some point? This one was just much bigger with really nasty consequence possible.

    Whippet set this one off a couple of years ago (which I then took advantage of to play silly buggers), much smaller and safer, but same in a way

    [​IMG]

    Stay safe out there guys!
     
  9. sbm

    sbm Dedicated Member
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    In conclusion, my little rule of thumb for minimizing dry/cold slab avalanche exposure, is wait. Powder fever costs lives. Wait for the storm to pass, wind to die down, the new snow to settle a bit. Wait for some other guinea pig to test it first! Hell, wait all the way until spring and uniform spring snowpack.

    And my little rule of thumb for minimizing wet/warm avalanche exposure, is DON'T wait. Get your ass out of bed EARLY in spring, and hit the corn snow well before it turns into warm porridge, that just wants to slop off the mountainside.
     
  10. AndrewA

    AndrewA Well-Known Member

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    ?fair weather skier!
     
  11. sbm

    sbm Dedicated Member
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    Ha, probably a fair accusation these days. But I aim to be more of a cautious poor weather skier, and a bolder fair weather one!
     
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  12. Ralph_Plow

    Ralph_Plow Active Member

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    Skiing wind loaded slopes is fine, but ski cutting on a convex directly after a fresh loading is as if they were trying to set something off. A dangerous game on a 1.8m pack (almost all wind load).

    I don't know the details, but I assume they had analysed the pack and known of the bonding issue, even less of a reason to get on the convex IMO, if they didn't know of the layer even less reason to be hitting the convex. It might have been possible, although risky, to enter the slope a little lower and not trigger at all.

    Again, wasn't there, don't know much more than "it happened", and the benefit of 20/20 hindsight is of course significant. I am curious as to the thought process though.
     
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  13. Ralph_Plow

    Ralph_Plow Active Member

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    Never have, figure if I think i have to cut it to be safe, may as well just pick another line. I have been in groups where someone more experienced than I has cut, never set anything of great consequence though.
     
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  14. Hully

    Hully Dedicated Member

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    The great outcome of this incident is that nobody was hurt or killed and it's got people talking across a heap of channels about the real risk of avalanche in the Australian backcountry. Knowing those involved they will have analysed their actions and the incident above and beyond anybody doing the same based on 2nd and 3rd party recounts, hence the detailed and honest report of the incident.
     
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  15. snowgum

    snowgum Dedicated Member

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    Scary fascinating stuff. I've seen pics of the slope involved.

    But to better learn from this, are you saying a well loaded 'concave' slope would have been OK?

    is there a recommended guide (page ref) for this type of slide pls?

    --------

    Just as a by the way, I noticed breakable crust yesterday at 1700-1745m,on very mellow, north/northeast aspects of Mt Stirling (-4pm). Quite soft snow underneath but a nasty 5-10 cm slab on top. Not fun to ski!

    Probably irrelevant but since we're talking layers not bonding. Cheers. Safe skiing guys.
     
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  16. Rabid K9

    Rabid K9 Dedicated Member
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    Know it was a wind loaded gully, but still amazed at the depth of the crown considering the preceding lean early season.
     
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  17. DPS Driver

    DPS Driver Dedicated Member

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    When I read it I couldn't help but wonder if it was an intentional ski cut or unintentional.

    Decent size release though. I've not seen many crown walls in Oz that depth. Glad all were safe.
     
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  18. sbm

    sbm Dedicated Member
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    Good enough for Mt Hutt Ski Patrol over the ditch apparently: "Ski cuts in the Mt. Hutt ski field released 1-2 meter deep wind slabs in N-NE aspects, elevation 1700 meters, and on slope angles at and greater than 35 degrees....Failure layers were a density change in the new snow, likely from the increasing winds and temperature changes"

    Business as usual in NZ haha!
     
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  19. sbm

    sbm Dedicated Member
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    Though Kiwi ski patrol are perhaps not the best role models. I still have a classic avy report from Craigieburn a few years ago saved somewhere, where they triggered a deep wet slide on the whole Hamilton Face that buried the bottom tow and closed the field for the day, that propagated from the pit they were digging! Bet that one caused some brown pants.
     
  20. telecrag

    telecrag Part of the Furniture
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    There was a day when the head patroller went down in a ski cut inbounds. He was OK, much mirth for the rest of the season. Its a standard practice.

    I find it fun on things that are not too brutal, and have used it as mentioned before to check a slope that I was 70/30 on. But I would not try it on something as big as this.
     
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  21. Ralph_Plow

    Ralph_Plow Active Member

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    It's ski patrols job to reduce avalanche risk so punters can ski around in relative safety. Triggering slides removes load.

    Not sure you can compare that to a small group travelling in a remote area.
     
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  22. Ralph_Plow

    Ralph_Plow Active Member

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    All wind load.....ding ding ding ding ding!!!
     
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  23. Red_switch

    Red_switch Part of the Furniture
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    Are folks in Australia wearing beacons yet?
     
  24. Ralph_Plow

    Ralph_Plow Active Member

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    My BC travel has been pretty limited for some years, but pre 2010 my group of BC friends always took gear. Trained at the local park beforehand and everything. Probably what happens when you do a lot of BC in Japan in the northern season at the time in high risk conditions (as it always seem to be there). Habits tend to carry over. It was a rarity though among other groups, and probably still is.

    Happy to be accused of overkill in this area.
     
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  25. DPS Driver

    DPS Driver Dedicated Member

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    The alarm bells may have been ringing but doesn't mean they were being heard.

    Benefit of the doubt though and good early season warning to take care out there.
     
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  26. Ralph_Plow

    Ralph_Plow Active Member

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    My thoughts too, can't judge unless you were there, but as I said the thought process is of interest.
     
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  27. DPS Driver

    DPS Driver Dedicated Member

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    I'd have to say yes mostly. We've had a couple of incidents over here over the past couple of years and the message is getting out.
     
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  28. DPS Driver

    DPS Driver Dedicated Member

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    I'm happy that it spread so quickly on social media, to send a timely early season reminder that big sh!t can happen here in Australia as it does OS.
    No one got caught and all came home safe. Good day by all accounts and hopefully the awareness has increased.
     
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  29. Red_switch

    Red_switch Part of the Furniture
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    Cool. Good to hear. The only really quantitative numbers on beacon use I've seen for NZ are a bit disturbing/disappointing.
     
  30. Undies

    Undies Part of the Furniture
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    I'm curious about how deep some of the leeward skiing would be getting in some of these places like the main range? Regular waist deep fun when the wind blows hard enough?
     
  31. sbm

    sbm Dedicated Member
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    Nah, in my experience wind deposited snow never gets proper deep (skiing-wise). The snowflakes get so smashed into small crystals by the wind they pack in really dense and you don't sink in that far on skis. For waist deep you need big snowflakes falling in calm conditions (probably below the treeline)
     
  32. Red_switch

    Red_switch Part of the Furniture
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    You need to spend more time in couloirs.
     
  33. telecrag

    telecrag Part of the Furniture
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    Ive experience the odd thigh deep, but generally agree, the snow compacts very quickly here.
     
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  34. sbm

    sbm Dedicated Member
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    Sigh, don't we all.

    Also steeper slopes definitely ski deeper as well. Because of maths and trigonometry and all that. 35 degree slope angle adds about 20% to your experienced snow depth! Also you uphill leg is closer to the snow surface so it's easier to claim "thigh deep"
     
  35. GS

    GS Addicted Member
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    I often experience chest deep when I'm flailing around trying to get right side up again
     
    #35 GS, Jul 14, 2017
    Last edited: Jul 14, 2017
  36. Red_switch

    Red_switch Part of the Furniture
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    depends on sloughing! snow likes to fall off things!

    But yeah, there's a reason Elevator at the Remarkables is such a damn good line.
     
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  37. telecrag

    telecrag Part of the Furniture
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    You so need to take up tele!
     
  38. Undies

    Undies Part of the Furniture
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    That's the very reason I inflate my ABS backpack when I get off the V8 at Perisher.
     
  39. GS

    GS Addicted Member
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    LOL :thumbs:
     
  40. Ralph_Plow

    Ralph_Plow Active Member

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    Nobody needs that shit.
     
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  41. Ralph_Plow

    Ralph_Plow Active Member

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    ABS, so old skool, all about the jet fan these days.
     
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  42. telecrag

    telecrag Part of the Furniture
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    My snow deeper than your snow!
     
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  43. Ralph_Plow

    Ralph_Plow Active Member

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    My armpits less smelly!
     
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  44. Undies

    Undies Part of the Furniture
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    Next you'll be telling me my flouro onesie aint cool.
     
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  45. telecrag

    telecrag Part of the Furniture
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    That will always be cool.
     
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  46. Gimp

    Gimp Dedicated Member
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    Yes when conditions require and generally only when hitting the Western Faces
     
  47. piolet

    piolet Old And Crusty
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    IME not really
    But you need perspective of who is out where doing what. A massive amount of those out are fair weather folk not on steeps and certainly not entertaining ski cuts like that.
    Although the ignorance can run deep even in the of steady advice from friends :rolleyes:
     
  48. telecrag

    telecrag Part of the Furniture
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    My last thought is quite likely to be

    ooops

    Or something like that.
     
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  49. Telemark Phat

    Telemark Phat Part of the Furniture
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    Its almost unnecessary because of,...

    We have small windows of avalanche risk, almost always during severe weather. Ice, weather and difficulty in navigating poor weather are much greater risks in Australia than Avalanche. Plenty of people carry them to maintain good habits.
     
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  50. CarveMan

    CarveMan aussieskier.com
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    I wear a beacon whenever touring in Oz, mainly because I have one and I'd feel a bit silly if I got buried in an Avalanche without it. I've skied this line, and the one that claimed the two boarders a couple of years ago, but in conditions that were completely safe. I definitely have my avvie brain turned on whenever touring in Oz.
     
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