Comparing Avalanche Decision Frameworks Using Accident Data from the United States

Abstract

ABSTRACT: In recent years, a number of decision-making frameworks have been developed to help European recreationists make better decisions in avalanche terrain. This study evaluated how well these frameworks might perform in North America by comparing four of them (the Reduction Method, NivoTest, Stop-or-Go, and the SnowCard) and one very simple decision strategy (based on obvious clues) against 33 years of avalanche accident data from the United States. We evaluated decision frameworks across three attributes that affect their usefulness: 1) the number of accidents prevented by each method, 2) the range of terrain available under each method (mobility), and 3) ease of use. Using binomial comparisons, we found that the preventive validity of these frameworks was statistically invariant to the level of training of the accident party, their recreation activity, and the type of slab released by the accident. In contrast, we found a generally significant sensitivity to avalanche cli-mate, with most frameworks being significantly more conservative in maritime climates. And we found that most of these frameworks perform poorly at low and moderate avalanche hazard, which accounts for about 20 % of all accidents. By computing a utility function that incorporated preventive validity, mobility and ease of use, we found that the decision method based on obvious clues was optimal in the largest number of cases. Even when combined with the risk reduction provided by mitigation measures such as wearing avalanche transceivers and exposing one person at a time to the hazard, simpler methods ap-pear to be superior to more complex decision methods.