Articles | Volume 15, issue 7
https://doi.org/10.5194/tc-15-3293-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/tc-15-3293-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
16 Jul 2021
Research article |
| 16 Jul 2021
| 16 Jul 2021
Avalanche danger level characteristics from field observations of snow instability
WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland
Christoph Mitterer
Avalanche Forecasting Service Tyrol, Innsbruck, Austria
Benjamin Reuter
Centre d'Etude de la Neige, CEN, CNRM, MétéoFrance, Grenoble, France
Frank Techel
WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland
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Amelie Fees, Alec van Herwijnen, Michael Lombardo, Jürg Schweizer, and Peter Lehmann
Nat. Hazards Earth Syst. Sci., 24, 3387–3400, https://doi.org/10.5194/nhess-24-3387-2024, https://doi.org/10.5194/nhess-24-3387-2024, 2024
Short summary
Short summary
Glide-snow avalanches release at the ground–snow interface, and their release process is poorly understood. To investigate the influence of spatial variability (snowpack and basal friction) on avalanche release, we developed a 3D, mechanical, threshold-based model that reproduces an observed release area distribution. A sensitivity analysis showed that the distribution was mostly influenced by the basal friction uniformity, while the variations in snowpack properties had little influence.
Frank Techel, Stephanie Mayer, Ross S. Purves, Günter Schmudlach, and Kurt Winkler
Nat. Hazards Earth Syst. Sci. Discuss., https://doi.org/10.5194/nhess-2024-158, https://doi.org/10.5194/nhess-2024-158, 2024
Revised manuscript accepted for NHESS
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We evaluate fully data- and model-driven predictions of avalanche danger in Switzerland and compare them with human-made avalanche forecasts as a benchmark. We show that model predictions perform similarly to human forecasts calling for a systematic integration of forecast chains into the forecasting process.
Karsten Müller, Frank Techel, and Christoph Mitterer
Nat. Hazards Earth Syst. Sci. Discuss., https://doi.org/10.5194/nhess-2024-48, https://doi.org/10.5194/nhess-2024-48, 2024
Preprint under review for NHESS
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Avalanche forecasting is crucial for mountain safety. Tools like the European Avalanche Danger Scale and Matrix set standards for forecasters, but consistency still varies. We analyzed the use of the EAWS Matrix, aiding danger level assignment. Our analysis shows inconsistencies, suggesting further need for refinement and training.
Stephanie Mayer, Frank Techel, Jürg Schweizer, and Alec van Herwijnen
Nat. Hazards Earth Syst. Sci., 23, 3445–3465, https://doi.org/10.5194/nhess-23-3445-2023, https://doi.org/10.5194/nhess-23-3445-2023, 2023
Short summary
Short summary
We present statistical models to estimate the probability for natural dry-snow avalanche release and avalanche size based on the simulated layering of the snowpack. The benefit of these models is demonstrated in comparison with benchmark models based on the amount of new snow. From the validation with data sets of quality-controlled avalanche observations and danger levels, we conclude that these models may be valuable tools to support forecasting natural dry-snow avalanche activity.
Elisabeth D. Hafner, Frank Techel, Rodrigo Caye Daudt, Jan Dirk Wegner, Konrad Schindler, and Yves Bühler
Nat. Hazards Earth Syst. Sci., 23, 2895–2914, https://doi.org/10.5194/nhess-23-2895-2023, https://doi.org/10.5194/nhess-23-2895-2023, 2023
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Oftentimes when objective measurements are not possible, human estimates are used instead. In our study, we investigate the reproducibility of human judgement for size estimates, the mappings of avalanches from oblique photographs and remotely sensed imagery. The variability that we found in those estimates is worth considering as it may influence results and should be kept in mind for several applications.
Oscar Dick, Léo Viallon-Galinier, François Tuzet, Pascal Hagenmuller, Mathieu Fructus, Benjamin Reuter, Matthieu Lafaysse, and Marie Dumont
The Cryosphere, 17, 1755–1773, https://doi.org/10.5194/tc-17-1755-2023, https://doi.org/10.5194/tc-17-1755-2023, 2023
Short summary
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Saharan dust deposition can drastically change the snow color, turning mountain landscapes into sepia scenes. Dust increases the absorption of solar energy by the snow cover and thus modifies the snow evolution and potentially the avalanche risk. Here we show that dust can lead to increased or decreased snowpack stability depending on the snow and meteorological conditions after the deposition event. We also show that wet-snow avalanches happen earlier in the season due to the presence of dust.
Bastian Bergfeld, Alec van Herwijnen, Grégoire Bobillier, Philipp L. Rosendahl, Philipp Weißgraeber, Valentin Adam, Jürg Dual, and Jürg Schweizer
Nat. Hazards Earth Syst. Sci., 23, 293–315, https://doi.org/10.5194/nhess-23-293-2023, https://doi.org/10.5194/nhess-23-293-2023, 2023
Short summary
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For a slab avalanche to release, the snowpack must facilitate crack propagation over large distances. Field measurements on crack propagation at this scale are very scarce. We performed a series of experiments, up to 10 m long, over a period of 10 weeks. Beside the temporal evolution of the mechanical properties of the snowpack, we found that crack speeds were highest for tests resulting in full propagation. Based on these findings, an index for self-sustained crack propagation is proposed.
Stephanie Mayer, Alec van Herwijnen, Frank Techel, and Jürg Schweizer
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Short summary
Short summary
Information on snow instability is crucial for avalanche forecasting. We introduce a novel machine-learning-based method to assess snow instability from snow stratigraphy simulated with the snow cover model SNOWPACK. To develop the model, we compared observed and simulated snow profiles. Our model provides a probability of instability for every layer of a simulated snow profile, which allows detection of the weakest layer and assessment of its degree of instability with one single index.
Cristina Pérez-Guillén, Frank Techel, Martin Hendrick, Michele Volpi, Alec van Herwijnen, Tasko Olevski, Guillaume Obozinski, Fernando Pérez-Cruz, and Jürg Schweizer
Nat. Hazards Earth Syst. Sci., 22, 2031–2056, https://doi.org/10.5194/nhess-22-2031-2022, https://doi.org/10.5194/nhess-22-2031-2022, 2022
Short summary
Short summary
A fully data-driven approach to predicting the danger level for dry-snow avalanche conditions in Switzerland was developed. Two classifiers were trained using a large database of meteorological data, snow cover simulations, and danger levels. The models performed well throughout the Swiss Alps, reaching a performance similar to the current experience-based avalanche forecasts. This approach shows the potential to be a valuable supplementary decision support tool for assessing avalanche hazard.
Frank Techel, Stephanie Mayer, Cristina Pérez-Guillén, Günter Schmudlach, and Kurt Winkler
Nat. Hazards Earth Syst. Sci., 22, 1911–1930, https://doi.org/10.5194/nhess-22-1911-2022, https://doi.org/10.5194/nhess-22-1911-2022, 2022
Short summary
Short summary
Can the resolution of forecasts of avalanche danger be increased by using a combination of absolute and comparative judgments? Using 5 years of Swiss avalanche forecasts, we show that, on average, sub-levels assigned to a danger level reflect the expected increase in the number of locations with poor snow stability and in the number and size of avalanches with increasing forecast sub-level.
Achille Capelli, Franziska Koch, Patrick Henkel, Markus Lamm, Florian Appel, Christoph Marty, and Jürg Schweizer
The Cryosphere, 16, 505–531, https://doi.org/10.5194/tc-16-505-2022, https://doi.org/10.5194/tc-16-505-2022, 2022
Short summary
Short summary
Snow occurrence, snow amount, snow density and liquid water content (LWC) can vary considerably with climatic conditions and elevation. We show that low-cost Global Navigation Satellite System (GNSS) sensors as GPS can be used for reliably measuring the amount of water stored in the snowpack or snow water equivalent (SWE), snow depth and the LWC under a broad range of climatic conditions met at different elevations in the Swiss Alps.
Veronika Hutter, Frank Techel, and Ross S. Purves
Nat. Hazards Earth Syst. Sci., 21, 3879–3897, https://doi.org/10.5194/nhess-21-3879-2021, https://doi.org/10.5194/nhess-21-3879-2021, 2021
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How is avalanche danger described in public avalanche forecasts? We analyzed 6000 textual descriptions of avalanche danger in Switzerland, taking the perspective of the forecaster. Avalanche danger was described rather consistently, although the results highlight the difficulty of communicating conditions that are neither rare nor frequent, neither small nor large. The study may help to refine the ways in which avalanche danger could be communicated to the public.
Bastian Bergfeld, Alec van Herwijnen, Benjamin Reuter, Grégoire Bobillier, Jürg Dual, and Jürg Schweizer
The Cryosphere, 15, 3539–3553, https://doi.org/10.5194/tc-15-3539-2021, https://doi.org/10.5194/tc-15-3539-2021, 2021
Short summary
Short summary
The modern picture of the snow slab avalanche release process involves a
dynamic crack propagation phasein which a whole slope becomes detached. The present work contains the first field methodology which provides the temporal and spatial resolution necessary to study this phase. We demonstrate the versatile capabilities and accuracy of our method by revealing intricate dynamics and present how to determine relevant characteristics of crack propagation such as crack speed.
Elisabeth D. Hafner, Frank Techel, Silvan Leinss, and Yves Bühler
The Cryosphere, 15, 983–1004, https://doi.org/10.5194/tc-15-983-2021, https://doi.org/10.5194/tc-15-983-2021, 2021
Short summary
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Satellites prove to be very valuable for documentation of large-scale avalanche periods. To test reliability and completeness, which has not been satisfactorily verified before, we attempt a full validation of avalanches mapped from two optical sensors and one radar sensor. Our results demonstrate the reliability of high-spatial-resolution optical data for avalanche mapping, the suitability of radar for mapping of larger avalanches and the unsuitability of medium-spatial-resolution optical data.
Bettina Richter, Alec van Herwijnen, Mathias W. Rotach, and Jürg Schweizer
Nat. Hazards Earth Syst. Sci., 20, 2873–2888, https://doi.org/10.5194/nhess-20-2873-2020, https://doi.org/10.5194/nhess-20-2873-2020, 2020
Short summary
Short summary
We investigated the sensitivity of modeled snow instability to uncertainties in meteorological input, typically found in complex terrain. The formation of the weak layer was very robust due to the long dry period, indicated by a widespread avalanche problem. Once a weak layer has formed, precipitation mostly determined slab and weak layer properties and hence snow instability. When spatially assessing snow instability for avalanche forecasting, accurate precipitation patterns have to be known.
Frank Techel, Karsten Müller, and Jürg Schweizer
The Cryosphere, 14, 3503–3521, https://doi.org/10.5194/tc-14-3503-2020, https://doi.org/10.5194/tc-14-3503-2020, 2020
Short summary
Short summary
Exploring a large data set of snow stability tests and avalanche observations, we quantitatively describe the three key elements that characterize avalanche danger: snowpack stability, the frequency distribution of snowpack stability, and avalanche size. The findings will aid in refining the definitions of the avalanche danger scale and in fostering its consistent usage.
Cited articles
Bakermans, L., Jamieson, B., Schweizer, J., and Haegeli, P.: Using stability tests and regional avalanche danger to estimate the local avalanche danger, Ann. Glaciol., 51, 176–186, https://doi.org/10.3189/172756410791386616, 2010.
Bellaire, S., Jamieson, B., and Schweizer, J.: When to dig? Thoughts on estimating slope stability, Proceedings ISSW 2010, International Snow Science Workshop, Lake Tahoe, CA, USA, 17–22 October 2010, 424–430, 2010.
Breiman, L., Friedman, J. H., Olshen, R. A., and Stone, C. J.: Classification and regression trees, CRC Press, Boca Raton, USA, 368 pp., 1998.
EAWS: Avalanche Danger Scale, available at: https://www.avalanches.org/standards/avalanche-danger-scale/, last access: 30 March 2021.
Fierz, C., Armstrong, R. L., Durand , Y., Etchevers, P., Greene, E., McClung, D. M., Nishimura, K., Satyawali, P. K., and Sokratov, S. A.: The International Classification for Seasonal Snow on the Ground, HP-VII Technical Documents in Hydrology, IACS Contribution No 1, UNESCO-IHP, Paris, France, 90 pp., 2009.
Föhn, P.: Lawinen – kurzfristige Gefahrenbeurteilung (Prognose), Schweizerische Zeitschrift für Forstwesen, 145, 59–73, 1994.
Föhn, P. M. B.: The Rutschblock as a practical tool for slope stability evaluation, Symposium at Davos 1986 – Avalanche Formation, Movement and Effects, IAHS Publ., 162, 223–228, 1987.
Föhn, P. M. B. and Schweizer, J.: Verification of avalanche danger with respect to avalanche forecasting, in: Les apports de la recherche scientifique à la sécurite neige, glace et avalanche. Actes de Colloque, Chamonix, 30 May–3 June 1995, edited by: Sivardière, F., ANENA, Grenoble, France, 151–156, 1995.
Giraud, G., Lafeuille, J., and Pahaut, E.: Evaluation de la qualité de la prevision du risque d'avalanche, Symposium at Davos 1986 – Avalanche Formation, Movement and Effects, IAHS Publ., 162, 583–591, 1987.
Haladuick, S.: Relating field observations and snowpack tests to snow avalanche danger, MSc thesis, Department of Civil Engineering, University of Calgary, Calgary AB, Canada, 178 pp., 2014.
Harvey, S., Meister, R., Leuthold, H., and Allgöwer, B.: Local verification of the Swiss avalanche bulletin, Proceedings ISSW 1998, International Snow Science Workshop, Sunriver, Oregon, USA, 27 September–1 October 1998, 339–343, 1998.
Jamieson, B., Haegeli, P., and Schweizer, J.: Field observations for estimating the local avalanche danger in the Columbia Mountains of Canada, Cold Reg. Sci. Technol., 58, 84–91, https://doi.org/10.1016/j.coldregions.2009.03.005, 2009.
Jamieson, J. B.: The compression test – after 25 years, The Avalanche Review, 18, 10–12, 1999.
Lehning, M., Bartelt, P., Brown, R. L., Russi, T., Stöckli, U., and Zimmerli, M.: Snowpack model calculations for avalanche warning based upon a new network of weather and snow stations, Cold Reg. Sci. Technol., 30, 145–157, https://doi.org/10.1016/S0165-232X(99)00022-1, 1999.
Meister, R.: Country-wide avalanche warning in Switzerland, Proceedings ISSW 1994, International Snow Science Workshop, Snowbird, Utah, USA, 30 October–3 November 1994, 58–71, 1995.
Reuter, B. and Semmel, C.: Backcountry risk assessment based on terrain and snowpack characteristics, Proceedings ISSW 2018, International Snow Science Workshop, Innsbruck, Austria, 7–12 October 2018, 1632–1634, 2018.
Reuter, B., van Herwijnen, A., Veitinger, J., and Schweizer, J.: Relating simple drivers to snow instability, Cold Reg. Sci. Technol., 120, 168–178, https://doi.org/10.1016/j.coldregions.2015.06.016, 2015.
Reuter, B., Calonne, N., and Adams, E.: Shear failure of weak snow layers in the first hours after burial, The Cryosphere Discuss. [preprint], https://doi.org/10.5194/tc-2018-268, 2019.
Schweizer, J.: Rutschblock 73 – Verifikation der Lawinengefahr, Bergundsteigen – Zeitschrift für Risikomanagement im Bergsport, Oesterreichischer Alpenverein, Innsbruck, Austria, 12, 56–59, 2003.
Schweizer, J.: Verifikation des Lawinenbulletins, in: Schnee und Lawinen in den Schweizer Alpen. Winter 2004/2005. Wetter, Schneedecke und Lawinengefahr. Winterbericht SLF, edited by: Pielmeier, C., Aebi, M., and Schweizer, J., Eidg. Institut für Schnee- und Lawinenforschung SLF, Davos, Switzerland, 91–99, 2007.
Schweizer, J.: Predicting the avalanche danger level from field observations, Proceedings ISSW 2010, International Snow Science Workshop, Lake Tahoe, CA, USA, 17–22 October 2010, 162–165, 2010.
Schweizer, J. and Jamieson, J. B.: Snowpack properties for snow profile analysis, Cold Reg. Sci. Technol., 37, 233–241, https://doi.org/10.1016/S0165-232X(03)00067-3, 2003.
Schweizer, J. and Jamieson, J. B.: A threshold sum approach to stability evaluation of manual snow profiles, Cold Reg. Sci. Technol., 47, 50–59, https://doi.org/10.1016/j.coldregions.2006.08.011, 2007.
Schweizer, J. and Jamieson, J. B.: Snowpack tests for assessing snow-slope instability, Ann. Glaciol., 51, 187–194, https://doi.org/10.3189/172756410791386652, 2010.
Schweizer, J. and Wiesinger, T.: Snow profile interpretation for stability evaluation, Cold Reg. Sci. Technol., 33, 179–188, https://doi.org/10.1016/S0165-232X(01)00036-2, 2001.
Schweizer, J., Kronholm, K., and Wiesinger, T.: Verification of regional snowpack stability and avalanche danger, Cold Reg. Sci. Technol., 37, 277–288, https://doi.org/10.1016/S0165-232X(03)00070-3, 2003.
Schweizer, J., McCammon, I., and Jamieson, J. B.: Snowpack observations and fracture concepts for skier-triggering of dry-snow slab avalanches, Cold Reg. Sci. Technol., 51, 112–121, https://doi.org/10.1016/j.coldregions.2007.04.019, 2008.
Schweizer, J., Mitterer, C., Techel, F., Stoffel, A., and Reuter, B.: On the relation between avalanche occurrence and avalanche danger level, The Cryosphere, 14, 737–750, https://doi.org/10.5194/tc-14-737-2020, 2020.
Schweizer, J., Mitterer, C., Reuter, B., and Techel, F.: Field observations of snow instabilities, EnviDat [data set], https://doi.org/10.16904/envidat.222, 2021.
Simenhois, R. and Birkeland, K. W.: The Extended Column Test: Test effectiveness, spatial variability, and comparison with the Propagation Saw Test, Cold Reg. Sci. Technol., 59, 210–216, https://doi.org/10.1016/j.coldregions.2009.04.001, 2009.
Spiegel, M. R. and Stephens, L. J.: Schaum's Outline of Theory and Problems of Statistics, 3rd edn., Schaum's outline series, McGraw-Hill, New York, 538 pp., 1999.
Statham, G., Haegeli, P., Greene, E., Birkeland, K., Israelson, C., Tremper, B., Stethem, C., McMahon, B., White, B., and Kelly, J.: A conceptual model of avalanche hazard, Nat. Hazards, 90, 663–691, https://doi.org/10.1007/s11069-017-3070-5, 2018.
Stoffel, L. and Schweizer, J.: Guidelines for avalanche control services: organization, hazard assessment and documentation – an example from Switzerland, Proceedings ISSW 2008, International Snow Science Workshop, Whistler BC, Canada, 21–27 September 2008, 483–489, 2008.
Techel, F.: On consistency and quality in public avalanche forecasting – a data-driven approach to forecast verification and to refining definitions of avalanche danger, PhD thesis, Faculty of Science, University of Zurich, Zurich, Switzerland, 236 pp., https://doi.org/10.5167/uzh-199650, 2020.
Techel, F. and Pielmeier, C.: Automatic classification of manual snow profiles by snow structure, Nat. Hazards Earth Syst. Sci., 14, 779–787, https://doi.org/10.5194/nhess-14-779-2014, 2014.
Techel, F. and Schweizer, J.: On using local avalanche danger level estimates for regional forecast verification, Cold Reg. Sci. Technol., 144, 52–62, https://doi.org/10.1016/j.coldregions.2017.07.012, 2017.
Techel, F., Mitterer, C., Ceaglio, E., Coléou, C., Morin, S., Rastelli, F., and Purves, R. S.: Spatial consistency and bias in avalanche forecasts – a case study in the European Alps, Nat. Hazards Earth Syst. Sci., 18, 2697–2716, https://doi.org/10.5194/nhess-18-2697-2018, 2018.
Techel, F., Müller, K., and Schweizer, J.: On the importance of snowpack stability, the frequency distribution of snowpack stability, and avalanche size in assessing the avalanche danger level, The Cryosphere, 14, 3503–3521, https://doi.org/10.5194/tc-14-3503-2020, 2020.
van Herwijnen, A. and Jamieson, J. B.: Snowpack properties associated with fracture initiation and propagation resulting in skier-triggered dry snow slab avalanches, Cold Reg. Sci. Technol., 50, 13–22, https://doi.org/10.1016/j.coldregions.2007.02.004, 2007.
Wilks, D. S.: Statistical methods in the atmospheric sciences, 3rd ed., International Geophysics Series, Academic Press, San Diego, CA, USA, 467 pp., 2011.
Zeidler, A. and Jamieson, J. B.: A nearest-neighbour model for forecasting skier-triggered dry-slab avalanches on persistent weak layers in the Columbia Mountains, Canada, Ann. Glaciol., 38, 166–172, https://doi.org/10.3189/172756404781815194, 2004.
Short summary
Snow avalanches threaten people and infrastructure in snow-covered mountain regions. To mitigate the effects of avalanches, warnings are issued by public forecasting services. Presently, the five danger levels are described in qualitative terms. We aim to characterize the avalanche danger levels based on expert field observations of snow instability. Our findings contribute to an evidence-based description of danger levels and to improve consistency and accuracy of avalanche forecasts.
Snow avalanches threaten people and infrastructure in snow-covered mountain regions. To mitigate...
