New slope tests and evaluation methods

**AltaPowderDaze** · 11-10-2006, 08:12 PM

5 lemons: new evaluation method for go/no go decision making. basically it states that there are 5 factors present in unstable snowpacks. all five need not be present for avalanche but the more you have the more likely it is to be unstable.
http://snowpit.com/articles/lemons%20reprint%20copy.pdf

this next part was presented today by bruce tremper at the blasters clinic. this is how i recall it so hopefully flykdog will chime in with how he remembers it.

new info also presented at the issw brought to light the fact that our current stability tests are not effective enough. compression, shear and rutshblock tests are giving false positives to stability and people are getting suprised by the instability that follows. they discovered that these tests, while finding weak layers, are not adequately testing the energy in the snowpack. energy is easily seen when the snow cracks at your feet as you trek thru a wind pillow. the energy is informally quantified by how much effort was required and how far the crack runs/propogates. to further assess the energy, they developed a tests that would allow you to actually see the propogation along a given weak layer. the basic idea of the first one is to cut a meter long pit deeper than the suspected weak layer. you still isolate the back and sides but now your column is the full meter long instead of a shovel width. from there, you would initiate a compression or shovel shear test just as you usually would but start from one side. when the column shows the weak layer you check to see how far (from side to side) the collapse/shear has propogated. you may need to give the shovel another tap after the layer collapses to check for further propogation. in the second test, a similar column is cut and isolated along the top and one side. this column, however, runs parallel to the fall line or back up the slope. you then begin to isolate the third side from the bottom to the top until the slab comes off, similar to a tilt test. they are working on a way to quantify this one. it will likely be how far you saw up before it slides.

these are new to me but bruce seemed very optimistic by the data sets that the researchers had come up with. i'd like to hear what others from the issw or blasters clinic have to say about these.

also, the swiss have come up with a really interesting interactive cd that will be translated to english and given out free by sometime this winter. check back at the uac website to find out when they get a hold of it.

**summit** · 11-10-2006, 08:29 PM

I don't know that I'd call the lemons method that new... its been around several years... 4 years I think... I remember hearing a presentation on it two years ago. It is a REALLY neat system and well worth the read. Ian McCammon is an incredible person to hear talk.

The current thread on these topics is just a few posts down the page...
http://www.tetongravity.com/forums/s...ad.php?t=65318

More about the CD would be cool

**AltaPowderDaze** · 11-10-2006, 08:55 PM

thanks summit. i haven't had much time to hang out on the forums lately. that's all new info to me. my subscription to the avalanche review has stopped since i couldn't get them to change my address over either of my last two moves but i suppose the info would show up there first.