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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]

Abstract: In Italy, railways crossing the alpine valleys are a vital means of civil and commercial communications with the rest of Europe. The geomorphologic configuration and the climatic conditions, especially in winter and spring, can cause rock fall events resulting in railway service interruptions and damage to infrastructure and, in the worst case, to people. There were rock fall events at a slope adjacent to the Domodossola–Iselle railway, most recently in 2004. This paper evaluates the stability of a mountain slope and maps rock fall hazards through the modeling of potential runout trajectories. Traditional geological, geomorphological and geo-engineering surveys were combined with data derived from digital terrestrial photogrammetry. Stereo photographic pairs of rocky outcrops in inaccessible areas were acquired from a helicopter. Data from photogrammetry, topographic measurements and laser scanning were then integrated to build a digital model of the slope, to characterize the rock mass and block geometry, and to define possible runout trajectories. The geomatic methods used have yielded oriented stereo-images, orthophotos and precise digital models of rocky wedges. Geometrical and structural characteristics of slopes, such as joint attitude, spacing and persistence, and block volumes, were also derived. The results were used together with a deterministic limit equilibrium method to evaluate slope stability. We assessed the probabilistic distribution of rock fall end points and kinetic energy along the rock falling paths and existing barriers, and created a hazard map based on the spatial distribution of trajectories, rock fall transit density and kinetic energy. [Copyright &y& Elsevier]

Abstract: This paper deals with the problem of mountain river crossing in old towns whose urban morphology often prevents one from building a ramp to access the bridge. If this is the case, the proposed solution consists in designing a bridge which can be lifted when a flood occurs. Some bridges of this kind are actually on duty in the Italian Alps but all of them are moved by means of hydraulic jacks. A table bridge moved by the buoyancy force of the river water is suggested. The design concept is here specified for a real case where a floating bridge is placed in the position where a bridge moved by hydraulic jacks was built. This choice enables one to compare the two solutions under the same conditions. The simplicity and robustness of the design, as well as the possibility of fully automatic functioning without any external support (i.e. electric energy) lead the authors to state that the floating bridge suggested is preferable to a bridge lifted by means of hydraulic jacks. [Copyright &y& Elsevier]

Abstract: For the generation of susceptibility maps on medium scales (1:25,000 to 1:50,000) using statistical techniques, a reliable landslide inventory is needed, together with factor maps used as inputs. This paper compares landslide susceptibility maps obtained with the same methodology but using different landslide inventories: the official Italian landslide inventory GeoIFFI for the Lombardy Region and a recently mapped inventory (DF2001). The analysis included four main steps: (i) preparation of debris flow inventories using both random and spatial partitions and factor maps as explanatory variables; (ii) calculation of accountability and reliability indices for a preliminary susceptibility analysis and selection of an appropriate combination of the factor maps for detailed analysis; (iii) evaluation and validation of the obtained susceptibility maps; and (iv) comparison of the results and selection of the final map. The study area is located in the Valtellina Valley in the Central Italian Alps. The analysis identified highly susceptible areas of shallow landslides that may generate debris flows. It was demonstrated that more precisely delimited source areas for landslide-induced debris flows produce better susceptibility maps. However, the improvement of these maps was relatively limited when the inventories were randomly subdivided. Higher improvements were observed after the subdivision of the inventories into three geographical parts with different geomorphological characteristics. Although the modelling showed very similar results if evaluation is made using standard techniques, the spatial pattern of the susceptibility maps was highly variable and dependent on the combination of the factor maps used. [Copyright &y& Elsevier]

This paper describes bed profile and grain size distribution adjustments in a mountain river (Maso di Spinelle River, Italian Alps) stabilized by a sequence of boulder check-dams. The control works were originally designed to simulate the geometry of natural step-pool channels, where tumbling flow is the dominant hydraulic regime. Local scouring downstream of 29 drop structures is analysed through the use of nondimensional parameters where maximum scour depth and scour length are normalised to the drop height. Prior laboratory data reveal a pattern similar to field scours, where complex interactions occur between drop height, critical flow depth, and step spacing. The linkage between scour length and depth is also discussed. There seems to be a maximum step height for impinging jets that is approximately twice the drop height; this maximum may explain the upper limit of the steepness factor found in high-gradient step-pool streams. If such a maximum upper limit is confirmed by further studies, this may aid designs of foundation heights for transverse control works in steep channels. [Copyright &y& Elsevier]