In this work we report latest outcomes of 18 years-long dataset of monitoring in a very active debris flow-producing catchment, left tributary of the Cenischia valley, NW Italian Alps. The Mardarello catchment (6.61 km²), due to very unfavourable geological and geomorphologic conditions, can be considered a perennial source of debris (the bulk can be estimated at 2.6 106 m3) containing even large-sized blocks. It is incised in carbonatic, massive Mesozoic rocks ("Calcescisti con Pietre Verdi"), interbedded with clayey-arenitic schist, very steeply dipping downslope and widely overlied by deep-seated slope collapse deposits and partly by detrital talus. A north-south oriented fault system together with minor failures has resulted in a complex network of rock joints and cracks. The vegetal cover is developed down 2400 m elevation with pasture herbs and sparse shrubs. Around 2000 m a.s.l. Swiss mountain pine and Larix decidua partly colonize unstable slopes, below such altitude other kinds of Conifers are widely spread all over the catchment, still below chestnuts are also present; such biotopes are in part inherited from re-forestation works carried on for decades by the National Forestry Corps to hinder the soil degradation. The high drop between maximum basin altitude (Rocciamelone Mt., 3538 m a.s.l.) and the fan apex (900 m a.s.l.) is quickly attained over a stretch of only 4 km, with an average slope gradient of 60% and maximum of 80%. The average annual precipitation equals to 820 mm, monthly rainfall depth is highest in Autumn and Springtime, accounting as a whole for 62% of the yearly total. A 1-3 m thick snow mantle usually caps the slopes above 2500 m a.s.l. from half October to the end of June. In spite of reforestation and hydraulic works realized in recent years, debris flows (2-years return period between 1991-2011) still pose significant hazard to human settlements located downstream. In the last one hundred years, thanks to historical documents andon-site monitoring conducted by the CNR-IRPI 31 debris flow events which caused significant damages have been reported. Generally, the mass transport is dominated by channelized debris flow occurring during the summer season, without damages for settlements; nevertheless, major events in the past impacted on the national road at the valley bottom. Since July 1994 the Marderello catchment had been instrumented for a best knowledge of the triggering factors, debris flow dynamics and related effects, in such a severe mountain environment, also in the sight to suggest possible structural interventions for preventing or reducing future damage in the underlying Novalesa village and ensure safety to hundreds of resident and floating population (Tropeano et al., 1996). The rainfall monitoring network consists of four raingauges placed at different elevations, between 800 and 2854 m a.s.l.; others meteorological data (air moisture and temperature, atmospheric pressure, wind speed and direction) are provided by three MICROS® radio-transmitting stations located at 3150, 2150 and 830 m a.s.l.. In 2013 the monitoring system has been further improved and extended on the alluvial fan with the installation of one ultrasonic device and four geophones (at a distance of around 50 m reciprocally) in order to detect debris flow wave-fronts depth and time-to-arrival. To reduce the amount of recorded data, the original ground velocity signal measured by the geophones is transformed into a mean value of amplitude of the velocity signal second per second (Arattano, 1999). The research presently focuses on_ (i) the investigation of rainfall characteristics, as recorded to different catchment elevations, in the sight to detect rainfall triggering values for debris flow initiation (Turconi et al., 2008); (ii) the collection of debris-flow seismic data for the future development of a warning system for the lowest part of the alluvial fan. References. Arattano, M. (1999). On the use of seismic detectors as monitoring and warning systems for debris flows. Nat. Hazards, 20, 197-213. Tropeano D., Casagrande A., Luino F., Cescon F. (1996). Processi di mud-debris flow in Val Cenischia (Alpi Graie). Osservazioni nel bacino del T. Marderello. Quaderno di studi e di documentazione n°20 - Suppl. a GEAM Anno XXXIII, n. 2-3. Turconi L., Kumar De S., Tropeano D., Savio G. (2010). Slope failure and related processes in the Mt. Rocciamelone area (Cenischia Valley, Western Italian Alps), Geomorphology, Volume 114, Issue 3, 115-128.

Seismic monitoring has been profusely employed worldwide to detect vibrations induced by slope deformation and/or landslide detachment and propagation. The analysis of the seismic signal may provide, in fact, relevant information on the dynamics of unstable slopes. As an example, it may allow the identification of precursors of collapse before slope failure occurs and the estimation of volume and propagation velocity of rock-avalanches, rock-slides and debris-flows. In particular, the monitoring of several characteristics of debris-flows can be efficiently performed through the use of seismic devices. The passage of a debris-flow wave, in fact, induces strong ground vibrations that can be easily and clearly recorded by different types of ground vibration sensors (accelerometers, velocimeters, microphones). Since the monitoring of debris flow is fundamental for studying their propagation and hazard implications, many kind of sensors have been tested and employed to measure the parameters that might be relevant for debris-flow investigation and study. Itakura et al. (2005) provided an extended review on this topic. However, ground vibration sensors provide an important advantage, in comparison with other devices, since they can be installed at a safe distance from the channel bed and do not interfere with the passage of the debris flow. This overcomes an important shortcoming of other types of sensors, like ultrasonic gauges, videocameras or speedometers, which need to be hung over the channel and thus are more prone to be damaged by the flow during the event. The recording of ground vibrations produced by debris flows presents however some difficulties and problems that need to be addressed and solved, such as the large amount of data detected by the sensors that need to be safely recorded. The output signal of the most commonly employed seismic sensors (velocimeters) is in fact a voltage proportional to the ground oscillation velocity. The typical frequencies of this signal usually ranges from 10 to 80 Hz and since the acquisition device needs to operate at a sampling frequency greater than the Nyquist sampling rate, usually a precautionary sampling rate greater than 100 Hz is adopted. This might be a problem when the device used for data recording is a standard data-logger, because of its limited storage capability. To solve the problem it is common to implement at least two different recording frequencies_ a lower (no-event mode, NEM) recording frequency (usually 1Hz) employed to record the data during the periods when no debris flow is taking place and a higher (event mode, EM) recording frequency that is adopted when a debris flow occurs. For this purpose a threshold value has to be used that is associated to an algorithm that checks the variations of the signal recorde at low frequency to identify when it overcomes the threshold and switch the recording from NEM to EM. Two different techniques of transformation have been applied so far to the original ground velocity signal measured by the geophone to obtain a lower recording frequency (usually 1Hz) and reduce the amount of recorded data_ (i) the transformation of the velocity signal into amplitude (Arattano, 1999) and (ii) the transformation into impulses (Abancò et al., 2012). The availability of high frequency monitoring data improves considerably the detection of debris-flows and the chances of their correct identification, as it occurs for other types of mass movements. Suriñach et al. (2005), as an example, pointed out that the spectrogram for a station that is approached by a sliding mass exhibits a triangular time/frequency signature, due to an increase over time in the higher-frequency constituents, that can be reliably identified. Recently, also Feng (2012) was able to extract a trapezoidal time-frequency seismic signature for a landslide-dam breach. A new experimental monitoring station has been developed and installed inside an instrumented catchment to compare advantages and limits of the two methods for lowering the recording frequency to 1 Hz (calculation of amplitude and measurement of impulses). The station is also aimed to investigate the possible existence of a triangular time/frequency signature for debris-flow and thus to integrate frequencies information in detection algorithms. The installation area is the Gadria catchment, located in the upper Venosta valley (Bolzano, Italy). The Gadria basin was chosen because of the relatively high frequency of debris flow occurrence (an average of 1-2 events per year) and because of the presence of a previous monitoring system realized by a consortium led by the Bolzano Province and composed by CNR IRPI and the Universities of Bolzano and Padova, with the support of EU-founded research projects (Comiti et al., 2013). The first purpose of the research is the definition of efficient threshold conditions that may allow to recognize the passage of a debris flow event on the basis of a low frequency signal. The threshold conditions will be employed to switch from NEM to EM recording frequency rates. Secondly, the detection algorithm will be tested integrating amplitude, impulses and high frequencies information. The expected results aim at contributing to the development of automatic detection, monitoring, and eventually early warning for debris-flow events. Acknowledgements. The authors wish to thank the Company SIAP+MICROS S.r.l. for having provided the monitoring equipment and its personnel (Marco Del Missier, Stefano Perin and Massimiliano Sanna) for the support in the development of the hardware and software components. References Abancó C., Hürlimann M., Fritschi B., Graf C., Moya J. (2012). Transformation of Ground Vibration Signal for Debris-Flow Monitoring and Detection in Alarm Systems. Sensors, 12 (4), 4870-4891. Arattano, M. (1999). On the use of seismic detectors as monitoring and warning systems for debris flows. Nat. Hazards, 20, 197-213. ComitiF., Marchi L, Macconi P., Arattano M., Bertoldi G., Borga M., Brardinoni F., Cavalli M., D'Agostino V., Penna D. (2013). A new monitoring station for debris flows in the European Alps_ first observations in the Gadria basin. Submitted to Natural Hazards. Feng Z. (2012). The seismic signatures of the surge wave from the 2009 Xiaolin landslide-dam breach in Taiwan. Hydrol. Process., 26_ 1342-1351. Itakura Y., Inaba H., Sawada T. (2005). A debris-flow monitoring devices and methods bibliography, Nat. Hazards Earth Syst. Sci., 5, 971-977. Suriñach E., Vilajosana I., Khazaradze G., Biescas B., Furdada G., and Vilaplana J. M. (2005). Seismic detection and characterization of landslides and other mass movements. Nat. Hazards Earth Syst. Sci., 5, 791-798.

The Monte Rosa east face (Macugnaga, Italian Alps) is one of the highest flanks in the Alps. Steep hanging glaciers and permafrost cover large parts of the wall. Since the end of the Little Ice Age (about 1850) the Monte Rosa east face is undergoing a progressive reduction of its ice cover; moreover new instability phenomena related to permafrost degradation and rapid deglaciation have been occurring since over a decade ago. The progressive destabilization of high-mountain faces is a consequence of many factors, such as topography, geological and structural conditions, intense freeze-thaw activity and oversteepened slopes from glacial erosion. Two major events, an ice avalanche occurred in August 2005 and a rock avalanche occurred in April 2007 are briefly described in this paper. In both cases, the accumulation area was located on the Belvedere Glacier at the foot of the Monte Rosa east face. A 3D dynamic model (DAN3D) was applied in order to back analyze the runout of the events, enabling the calibration of the input parameters for the assumed rheological models.

Climate changes are more and more attracting the attention of the scientific community because of their direct impacts on geomorphic systems and human activities. A number of studies are currently under way to investigate the evolution of high elevation environments, which proved to be particularly sensitive to climate changes and point to increased in instability in areas of cryosphere occurrence. The here presented research has been developed in the framework of the Alcotra project n.56 "GlaRiskAlp", by CNR-IRPI Torino in collaboration with the DST Torino - GeoSitLab laboratory and is aimed to the validation of an integrated geomatic approach for the evaluation of geomorphologic changes, and related hazards, in glacial and periglacial areas, in the contest of present climatic trends. The proposed approach is based on the coupling of remote sensing techniques and field surveys, in particular digital aerial photogrammetry and satellite imagery, terrestrial scanning LiDAR, and GNSS survey. High-resolution terrestrial LiDAR acquisition, processing and interpretation are used to map periglacial areas in the three dimensions. Laser-generated models offer a visualization tool that, through the comparison of DEMs of different years, allow to detect and to interpret even small geomorphologic changes in time. GNSS-networks are suitable tools for detecting changes over larger surfaces, or horizontal ones. Digital aerial photogrammetry and satellite images can be used to create ortophotos and DTMs of different years, allowing the reconstruction of main geomorphologic changes over the last 50 years. The proposed approach has been applied to case studies of the Piemonte region (Western Italian Alps).

In questo lavoro si presenta un'analisi dell'applicabilità di alcune tecniche geomatiche per il monitoraggio di settori a marcata dinamicità geomorfologica. La finalità ultima è quella di riconoscere in modo tempestivo i segnali dell'insorgere di un'eventuale instabilità che possano evolvere in situazioni di rischio. Il contributo specifico del gruppo di lavoro, composto da Università di Torino (GeoSITLab) e CNR-IRPI Torino, è stato finalizzato all'integrazione di una gamma di tecniche geomatiche ad alcuni settori dell'ambiente glacializzato piemontese, nell'ambito del progetto interreg alcotra n.56 GlaRiskAlp (Rischi Glaciali nelle Alpi Occidentali). In questo articolo si intende approfondire una parte dei risultati relativi al progetto in riferimento allo studio volto alla verifica dell'impiego di le tecniche di fotogrammetria aerea digitale e di posizionamento satellitare (GNSS).

Session 26, on landslides in cold regions, brought together scientists from around the world with representatives from Canada, China, France, Italy, New Zealand, Pakistan, Switzerland, and Russia. Presentations could be grouped into broad categories. The overarching keynote address by Stephan Gruber (Zurich) stressed the importance of understanding permafrost dynamics in the context of a changing climate as a key to landslide hazard assessments in cold regions. Stephan stressed concepts such as heterogeneity, non-linear trajectories of change, and unexpected results with respect to mountain permafrost, and that these conspire to make hazard analysis difficult. Chinese, Swiss Italian and Russian papers discussed aspects of landslides in cold soil, whereas the remaining papers discussed aspects cryospheric landslides (mainly) in rock. A subset of these last papers dealt with rock instabilities on the Mont Blanc massif.