Editing Avalanche (section)

=== Modeling ===
Attempts to model avalanche behaviour date from the early 20th century, notably the work of Professor Lagotala in preparation for the [[1924 Winter Olympics]] in [[Chamonix]].<ref name=Ancey>[http://lhe.epfl.ch/pdf/snow-avalanche.pdf Snow Avalanches], Christophe Ancey</ref> His method was developed by A. Voellmy and popularised following the publication in 1955 of his ''Ueber die Zerstörungskraft von Lawinen'' (On the Destructive Force of Avalanches).<ref>Voellmy, A., 1955. ''Ober die Zerstorunskraft von Lawinen''. Schweizerische Bauzetung (English: ''On the Destructive Force of Avalanches''. U.S. Dept. of Agriculture, Forest Service).</ref>

Voellmy used a simple empirical formula, treating an avalanche as a sliding block of snow moving with a drag force that was proportional to the square of the speed of its flow:<ref>[http://www.risknat.org/pages/programme_dep/docs/cemagref_etna/2002_Berthet-Rambaud.pdf Quantification de la sollicitation avalancheuse par analyse en retour du comportement de structures métalliques], page 14, ''Pôle Grenoblois d'études et de recherche pour la Prévention des risques naturels'', October 2003, in French</ref>

::<math> \textrm{Pref} = \frac {1} {2} \, { \rho} \, { v^2} \,\!</math>

He and others subsequently derived other formulae that take other factors into account, with the Voellmy-Salm-Gubler and the Perla-Cheng-McClung models becoming most widely used as simple tools to model flowing (as opposed to powder snow) avalanches.<ref name=Ancey />

Since the 1990s many more sophisticated models have been developed. In Europe much of the recent work was carried out as part of the SATSIE (Avalanche Studies and Model Validation in Europe) research project supported by the [[European Commission]]<ref>{{Cite web |url=http://www.leeds.ac.uk/satsie/ |title=SATSIE – Avalanche Studies and Model Validation in Europe |access-date=5 April 2008 |archive-date=12 June 2020 |archive-url=https://web.archive.org/web/20200612122550/http://www.leeds.ac.uk/satsie/ |url-status=dead}}</ref> which produced the leading-edge MN2L model, now in use with the ''Service Restauration des Terrains en Montagne'' (Mountain Rescue Service) in France, and D2FRAM (Dynamical Two-Flow-Regime Avalanche Model), which was still undergoing validation as of 2007.<ref name="final_report" /> Other known models are the SAMOS-AT avalanche simulation software<ref>{{cite web |url=http://arc.lib.montana.edu/snow-science/objects/issw-2009-0519-0523.pdf |title=Avalanche Simulation with SAMOS-AT |first1=Peter |last1=Sampl |first2=Matthias |last2=Granig |website=Archives and Special Collections – Montana State University Library |url-status=live |archive-url=https://web.archive.org/web/20220824211426/https://arc.lib.montana.edu/snow-science/objects/issw-2009-0519-0523.pdf |archive-date=Aug 24, 2022 }}</ref> and the RAMMS software.<ref>{{Cite web |title=Rapid Mass Movements System RAMMS |url=http://www.naturfare.no/_attachment/534838/binary/859980 |url-status=dead |archive-url=https://web.archive.org/web/20160304060348/http://www.naturfare.no/_attachment/534838/binary/859980 |archive-date=4 March 2016 |access-date=19 May 2015}}</ref>