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International audience; Taconnaz and Lautaret full-scale avalanche test-site and 3935 other French avalanche paths.

International audience; In recent years, the appearance of a large number of Open Source Webmapping solutions cause a significant increase in the use of dynamic maps for territory development. Each technology enjoys a large users and developers community that which leads to an improvement of the quality of the services (userfriendly, up to date). In this technological evolution climate, a Webmapping interface and a WMS service are being developed by Cemagref and the Ministry of Environment. The visibility of the service is guarantee by an access through various geographic portals. The Cemagref Webmapping application was developed in order to provide a public access of data produced under the EPA (the Permanent Avalanche Survey), the CLPA (the Localization Map of Avalanche Phenomena) and SSA (Sensitive Avalanche Paths Survey) in the Alps and the Pyrenees. The current and historical maps (dating from as early as the beginning as the 20th century) will be available on the Webmapping Application. These maps can be highlighted and completed by website information (www.avalanches.fr). By exploiting its current work on the interoperability between the different avalanche databases, Cemagref will take another step in the Webmapping application. Indeed, the cartographic server will be linked directly on these databases.

National audience; L'enquête permanente sur les avalanches (EPA) permet de suivre depuis plus d'un siècle l'activité avalancheuse de près de 3900 couloirs des Alpes et des Pyrénées. Cet article présente un bilan des avalanches enregistrées au cours de l'hiver 2008/09. Il complète les articles sur les conditions nivo-météorologiques et sur le bilan des accidents.

International audience; Radio frequency identification technology is used for monitoring the displacement of coarse particles in streams since the beginning of the 2000s. Passive integrated transponders (PIT tags) are small, cheap and long-lasting electronic tags that can be programmed with their own identification code. Initially used in environmental research for animal tracking, they have been deployed successfully in a variety of fluvial environments for coarse sediment tracing. Pioneering studies conducted in both semiarid and humid small upland streams with low intensity bedload transport gave recovery rates above 85% (Nichols 2004; Lamarre et al. 2005). Here we present an experiment of radio frequency sediment tracing implemented on a small braided mountain stream with a high intensity bedload transport and a wide active channel (mean active channel width: ~20 m). The study site is the Bouinenc Torrent, a tributary to the Bléone River in SE France that drains a 38 km² mountainous drainage basin of the Southern Prealps. In spring 2008, we deployed 451 tracers with b-axis ranging from 23 to 520 mm. Tracers were deployed along 8 cross sections located in the upstream part of the lowest 2.3 km of the stream. We developed a RFID detection system composed of an antenna and a reader unit; this system is characterized by a range of detection of 80 cm in optimal configuration. Two small intensity flow events occurred in June 2008 and entrained the tracers deployed in the most active part of the active channel. We mapped the position of the displaced tracers with a dGPS in July 2008. We obtained an overall recovery rate of 88%. The recovery rate calculated for the active tracers (those that were displaced after the flow events) was 76%. The projection of the tracer dispersion cloud on high resolution aerial photographs obtained with a drone allows us to calculate the distance of transport for each tracer. Mean and maximal distances of transport were respectively 796 m (+/- 53 m) and 2.3 km. We found several tracers on the last gravel bar located at the confluence with the Bléone River. This experiment allowed us to characterize (1) the influence of the grain size on the distance of transport, (2) the performance of theoretical critical shear stress calculations, and (3) the time-integrated bed-material transport of the torrent.

National audience; La crise avalancheuse de décembre 2008 est remarquable pour trois raisons : L'ampleur des phénomènes observés. En effet, ainsi que l'a établi l'article précédent, l'importante accumulation de neige froide et légère du haut en bas des versants, a permis à de nombreuses avalanches de parcourir d'importantes distances et a favorisé le développement d'aérosols conséquents. Les limites extrêmes des plus grosses avalanches connues répertoriées dans la CLPA ont ainsi parfois été largement dépassées. Le nombre important des phénomènes avalancheux. Durant ce mois de décembre 2008, sur sept communes du Queyras, au moins 34 phénomènes ont été répertoriés par les agents du RTM des Hautes Alpes comme nouveaux ou engendrant une modifi cation de leur tracé sur la CLPA. Les communes concernées sont : Aiguilles (2 avalanches), Abries (10 avalanches),Château-Ville-Vieille (2 avalanches),Ristolas (10 avalanches), Ceillac (3 avalanches),Arvieux (2 avalanches), Saint Véran (1 avalanche) et Molines en Queyras (4 avalanches). De plus, sur un nombre importantde sites, les avalanches ont atteint leur limite maximale connue sans les dépasser. Le caractère surprenant de certaines avalanches et la diversité dans les ampleurs. Des départs en zone boisée peu pentue ainsi que des dénivelés parcourus peu importants ont causé des dégâts sur des bâtiments à des endroits inattendus, alors que d'autres phénomènes plus habituels ont surpris en dépassant largement les ampleurs connues. Des avalanches jamais observées de mémoire d'homme se sont produites sur des petits versants dominant la vallée indépendamment de l'orientation. Cet article propose une analyse de cas d'avalanches remarquables durant cette crise.