Preprints
https://doi.org/10.5194/egusphere-2023-2921
https://doi.org/10.5194/egusphere-2023-2921
06 Dec 2023
 | 06 Dec 2023

How hard do we tap during snow stability tests?

Håvard Boutera Toft, Samuel V. Verplanck, and Markus Landrø

Abstract. This study examines the impact force applied from hand taps during Extended Column Tests (ECT), a common method of assessing snow stability. The hand-tap loading method has inconsistencies across the United States, Canadian, and Norwegian written standards, as well as inherent subjectivity. We developed a device, the “tap-o-meter”, to measure the force-time curves during these taps and collected data from 286 practitioners, including avalanche forecasters and mountain guides in Scandinavia, Central Europe, and North America. Peak forces and loading rates are the metrics chosen to quantitatively compare the data. The mean, median, and inner quartile peak forces are distinctly different for each loading step (wrist, elbow and shoulder), as are the loading rates. However, there is significant overlap across the range of measurements and examples of participants with higher force wrist taps than other participants' shoulder taps. This overlap challenges the reliability and reproducibility of ECT results, potentially leading to dangerous interpretations in avalanche decision-making, forecasting and risk assessments. Therefore, we recommend updating the standards for the ECT. We propose two viable paths for future action: (1) define a target impact force-time curve for each tap level and develop tools and training to minimize variability in tapping force (2) assess the significance of the information derived from the number of taps. If deemed not highly valuable, we should consider reverting to a simpler binary interpretation that focuses exclusively on crack propagation.

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Journal article(s) based on this preprint

16 Aug 2024
How hard do avalanche practitioners tap during snow stability tests?
Håvard B. Toft, Samuel V. Verplanck, and Markus Landrø
Nat. Hazards Earth Syst. Sci., 24, 2757–2772, https://doi.org/10.5194/nhess-24-2757-2024,https://doi.org/10.5194/nhess-24-2757-2024, 2024
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

Short summary
This study investigates inconsistencies in impact force during the Extended Column Tests (ECT)....
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