ISSW 2006 overview and relevance

ISSW 2006 (International Snow Services Workshop) was held at Telluride the first week of October. These workshops, which are held every two years, are truly international in nature. Topics usually include stability, education, instrumentation/avalanche control, avalanche forecasting, avalanche mapping, etc.

This year’s ISSW seemed to this observer to be a “coming together or synthesis” more than a forum on new ideas - with the exception of GIS mapping. This synthesis was most obvious in the areas of stability and education. Spatial variability has been has been a hot topic the last few ISSWs.

In my view there are really two different types of spatial variability - location specific (aspect, elevation, etc.) and variability on a particular apparently homogenous slope. This latter type of variability has been called “slope scale variability”. Slope scale variability is known to exist and is closely tied to slab release theory for human triggered slabs. It is known that on a slope of apparent uniformity there are stronger and weaker zones. The weak zones are potential trigger points for human-triggered slabs. While past ISSW’s have focused on documenting the existence of variable testing results owing to these weak spots, this year’s ISSW seemed to be moving in the direction of trying to understand just how much variability there is, statistically. At this point, because different methodology (different tests) have been used in different studies, exactly how much variability there is on apparently homogenous slopes is not yet known. Another limitation is that so far most of these studies have focused on surface hoar as the weak layer. I would think that variability at the slope scale is greatest with faceted crusts as the weak layer, but faceted crusts are also the most difficult to define because the structure of faceted crusts is so highly variable. Storm snow weak layers are more transient than surface hoar and faceted layers - the classic “persistent weak layers”. I would think that most storm snow weaknesses depend on changes of the grain type of falling snow and on wind changes during deposition. This latter shows up in snowpits as waves deposited in new snow – weak in places and stronger in others. So, right now it is probably accurate to say that when persistent weak layers are known to exist, one has to question the validity of the results obtained from any single test. For this reason, it has been suggested - and was stated again at this ISSW - that the goal of stability tests for the recreational user should be to confirm the significance of strengths and weaknesses that are delineated in avalanche forecasts. Realize that given that variability exists, the advantage of the avalanche forecasts is that they represent a significantly larger body of evidence regarding stability than any individual or group can obtain. Perhaps the best methodology is what has been described as “targeted sampling” trying to test where the snowpack is likely to be weakest. There is a Catch 22 operating here, though. This problem arises because there is no reason to expect that any particular location may not be weaker than most other locations. So, while no test is necessarily representative - particularly in the presence of persistent weak layers - it is still necessary to test to try to ascertain that one is not traveling through an area of particularly weak snow.

With regard to education, the main areas of interest are the widespread acceptance of McCammon and Schweizer’s “lemons” paper for evaluating the snowpack, the defining of terrain by both mapping and “ATES” definitions, and the development by the CAA of the “Avaluator” as a “Munter-like”, statistically supported decision-making tool, particularly for those with less experience. The ATES was created initially for Parcs Canada at the behest of the government following the high profile accidents in the winter of 2002-3. (For those of you that followed T-Tips following these accidents you may recall that there were strong discussions at the time. One of these accidents was highly controversial and most professionals would agree represented very poor risk management methodology. Conversations with several principals at ISSW demonstrated that many high profile CAC researchers share these views. Some reactionary personalities were so incensed and unable to logically process these accidents that intelligent conversation at the time was difficult. One particularly sick and child-like individual continues to follow me like bad gas, trying to hack my computer system. The FBI is currently tracking this individual.) Anyway, while it is still in the process of being “perfected”, the ATES is a paper that looks at the consequences side of the equation regarding risk in avalanche accidents. Well, it turns out that the Canadian government was “lurking” during these T-Tips discussions. An ATES-like definition and a “risk matrix” were both discussed at that time. The problem with proposed risk matrices was that they were not supported by statistics, so it was not possible to define the surfaces of the risk matrix. Statistics that Werner Munter used in creating his statistical Risk Reduction model were European and may not have been directly transferable to the US and Canada.

Enter the Canadian government with an infusion of $600,000 for the CAC to develop a risk matrix. Once the ATES was in place the axis opposite avalanche hazard made it possible to create such a statistical model. The Canadians studied some 250 (as I recall from a conversation at the CAC booth at ISSW) accidents and, then for the past two years, had both professional and recreationalists with less experience use this risk matrix and associated tools. The result was the “Avaluator” which is a very good risk reduction tool for less experienced recreationalists and for those who don’t have the time to invest in the process of gaining the requisite skills for effective risk-averse decisionmaking. Avaluator and the ATES are both being integrated into Canadian guidebooks and government mapping at this time.

The other really interesting developments at the ISSW were in the area of GIS mapping and graphical interfaces for avalanche forecasts. Though just beginning, and dependent on funding, expect to see a good deal of avalanche mapping in the near future based on the development of Google Earth and like-type models. These are likely to become integrated into avalanche forecast center products.