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Abstract: Experimental test sites are important to understand the physical flow processes occurring within an avalanche. They can be at different scale: laboratory or real scale. In Europe, a dozen of real-scale test sites have been realized, though at present only a few of them are still operative. The primary goal is to measure avalanche dynamical variables under controlled conditions. Not all the observed phenomena have been fully understood yet and more work is needed especially regarding small to medium avalanches. The aim of this paper is to present a new experimental test site at a real scale in order to study specific topics: the dynamics of small and medium avalanches, the avalanche release processes and the interaction between avalanche flows and obstacles. The test site, called Seehore, is located in Aosta Valley in the North-western Italian Alps. The slope, with an elevation difference of about 300m (from 2300 to 2570m asl), has a mean slope angle of about 28°. Avalanches are artificially released on a routine basis to secure the ski-runs, as the site is located within a ski resort (Monterosa Ski); they are usually dense slab avalanches of small or medium size, but also a powder cloud may occasionally form. The site is instrumented with a steel obstacle, described in details in a companion paper, which measures the effects of avalanches impacting on it. Before, during and after each artificial release physical properties of the snow in the avalanche release, track and deposition zones are recorded; front velocity, erosion and deposition mass are estimated by field surveys or by videogrammetry and terrestrial laser-scan measurements. [Copyright &y& Elsevier]

Snow avalanche hazard is one of the most critical aspects in the urbanization of mountainous areas. The risk from these natural phenomena can be reduced if proper countermeasures for reducing the danger or preventing avalanche triggering are taken. For instance, in the avalanche initiation zone, devices able to withstand snowpack gliding and prevent crack propagation can be installed. These can be classified as rigid (snow bridges) or flexible (snow net) structures, depending on the mechanisms involved under snow loading. In recent years, a new kind of structure called a snow umbrella, based on a net panel supported by rigid beams, has been designed and installed in the northwestern Italian Alps. As the real behavior of these structures is far from being simple to understand because of the complex interaction with snowpack movements, an umbrella was instrumented and monitored during the winter season of 2010-2011. The recorded data are used for testing two possible pressure distributions and evaluating the magnitude of the forces acting on the structure. Furthermore, a back-analysis allows validation of the assumptions taken during the design of the devices. The results are compared with commonly used guidelines, and further suggestions are proposed. [ABSTRACT FROM AUTHOR]