Item: A SPATIAL EXTRAPOLATION APPROACH TO SNOWPACK WEAK LAYER CRITICALITY ACROSS AVALANCHE RELEASE AREAS
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Title: A SPATIAL EXTRAPOLATION APPROACH TO SNOWPACK WEAK LAYER CRITICALITY ACROSS AVALANCHE RELEASE AREAS
Proceedings: Proceedings, International Snow Science Workshop, Whistler, BC, Canada, 2026
Authors:
- Frédéric Pourraz [ LISTIC – University Savoie Mont Blanc, Annecy, France ]
- Jill Chevalier [ LISTIC – University Savoie Mont Blanc, Annecy, France ]
- Alain Duclos [ data-avalanche.org association, Aussois, France ] [ ALEA (Avalanches: Location, Research and Action), Aussois, France ]
- Gaëlle Bourgeois [ Department of Savoie – Natural Hazards Service, Chambéry, France ]
- Cédric Perillat-Merceroz [ ALEA (Avalanches: Location, Research and Action), Aussois, France ]
Date: 2026-09-28
Abstract: Winter road serviceability in Savoie (northern French Alps) is ensured by the Natural Hazards Service of the Department in collaboration with the consulting firm ALEA. Their operational feedback has enabled the identification and geolocation of 252 avalanche release areas and flow paths likely to impact the road network. These areas are subject to continuous monitoring throughout the winter season, based on the real-time evaluation of the five criteria of the CRISTAL framework. This paper focuses specifically on the "Weak layer criticality" criterion, whose level is assessed using 2 main sources: observations of recent avalanche activity and performance of snowpack stability tests following the ROMANsns protocol, conducted several times per week all over the Savoie Department. However, this observation frequency does not allow full coverage of all 252 potential release areas. It is therefore necessary to extrapolate a criticality value for each site using data derived from spatially distant tests and/or observations. This extrapolation relies on a similarity computation incorporating various snow, meteorological, actinometric, and geospatial features. For some of these features, real-time observations and measures are insufficient; it is essential to model their temporal evolution from the beginning of the winter season. This approach makes it possible to assess whether snowpack stratigraphy across different sectors can be considered comparable. The resulting similarity is then used to estimate the "Weak layer criticality" criterion, at a given point in time, for each elevation band (at 100 m intervals) and for each aspect within the 252 studied areas. The CRISTAL method is subsequently applied to determine the required level of vigilance. The objective of this approach is not to replace human expertise with digital tools, but to enhance it. In a context of high spatial and temporal variability in snowpack stratigraphy, this tool is intended to support experts in their decision-making or to alert them to potentially hazardous situations that they might not have identified as such. Ultimately, the goal is to promote more objective decision-making regarding operational measures to be implemented on the road network of the Savoie Department
Object ID: ISSW2026_P4.39.pdf
DOI: https://doi.org/10.15788/1790099349
Language of Article: English
Presenter(s): Frédéric Pourraz
Keywords: Spatial extrapolation, Similarities, Snowpack criticality, Decision-making
Page Number(s): 1715 - 1722
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