Val Ferret Pilot Action Region: Grandes Jorasses Glaciers - An Open-Air Laboratory for the Development of Close-Range Remote Sensing Monitoring Systems

The Val Ferret valley (Courmayeur, Aosta Valley, Italy) was included as a Pilot Action Region (PAR) of the GreenRisk4Alps project since it is both a famous tourist location and a high-risk area for all types of mass movement processes. Typical natural hazards that endanger this PAR are debris flows and avalanches, sometimes connected to ice collapses from the glaciers of the Mont Blanc massif. Thanks to the steep sides of the valley and widespread alluvial channels, these events can reach the valley floor, where public roads, villages and touristic attractions are located. This article presents the main challenges of natural hazard management in the Val Ferret PAR, as well as the role of forestry and protective forests in the Aosta Valley Autonomous Region. As an example of good practice, the monitoring systems of the Planpincieux and Grandes Jorasses glaciers are presented. Recently, these glaciers have become an open-air laboratory for glacial monitoring techniques. Many close-range surveys have been conducted here, and a permanent network of monitoring systems that measure the surface deformation of the glaciers is currently active

Close-Range Sensing of Alpine Glaciers

Glacial processes can have a strong impact on human activities in terms of hazards and freshwater supply. Therefore, scientific observation is fundamental to understand their current state and possible evolution. To achieve this aim, various monitoring systems have been developed in the last decades to monitor different geophysical and geochemical properties. In this manuscript, we describe examples of close-range monitoring sensors to measure the glacier dynamics: (i) terrestrial interferometric radar, (ii) monoscopic time-lapse camera, (iii) total station, (iv) laser scanner, (v) ground-penetrating radar and (vi) structure form motion. We present the monitoring applications in the Planpincieux and Grandes Jorasses glaciers, which are located in the touristic area of the Italian side of the Mont Blanc massif. In recent years, the Planpincieux-Grandes Jorasses complex has become an open-air research laboratory of glacial monitoring techniques. Many close-range surveys have been conducted in this environment and a permanent network of monitoring systems that measures glacier surface deformation is presently active

The use of unmanned aerial vehicles (UAVs) for engineering geology applications

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Dynamics of alpine glaciers large instabilities: results and open problems

&amp;lt;p&amp;gt;The study of glacier instabilities can be very useful, particularly when the activation of large ice avalanches can be dangerous for several elements at risk down-valley. This critical condition characterizes a growing number of glaciers in the Alps, where the distance between infrastructures, tourist areas and glaciers are minimal. The tragedy that occurred in Marmolada in 2022 is an example of the impact that an ice avalanche can have on a highly frequented area. In several recent studies, glacier-related instabilities are based on approaches similar to the ones adopted for landslides; in particular, the use of high-rate monitoring systems is fundamental for a characterization of the surficial movement of the glacier and its activity. The presence of an acceleration phase is often a precursor of the fall of the unstable ice chunk, and that is why the use of high-rate monitoring systems can be adopted for early warning purposes. The availability of similar data also allows a deeper knowledge of the processes that characterize the evolution of glaciers. Up to the present, the limited presence of permanent survey systems has prevented a more detailed study of the dynamics that control the evolution of glaciers. Recent monitoring solutions adopted to manage the ice-avalanche-related risk in the Alps represent an excellent opportunity to reduce this gap. The Grand Jorasses (Italian side of the Mont Blanc massif) open-field laboratory for the development of monitoring systems is an interesting example of this recent opportunity. The presence of cold (Whymper serac) and temperate (Planpincieux glacier) monitored glaciers is also important for better evaluating the impact of water at the bedrock-ice interface on the stability of hanging glaciers. The results obtained in the Grand Jorasses open-field laboratory pointed out the high complexity of temperate glaciers due to the variety of triggers that can activate large ice falls. The restricted access to the site for safety reasons limited the direct measurement of important parameters and led to the adoption of proximal remote sensing solutions. Thanks to the acquired data, a conceptual model of the glaciers&amp;#039; dynamics have been developed and adopted for better risk assessment.&amp;lt;/p&amp;gt;</jats:p

Numerical modelling of ice avalanches from the Planpincieux glacier (Italy)

&amp;lt;p&amp;gt;Forward simulations of ice avalanches are important to inform risk management. However, the reliability of such simulations often suffers from the dependency of model parameters on the process magnitude, hampering the simulation of unprecedented events in a given area. We suggest a reliable, straightforward and practically applicable work flow for the forward simulation of ice avalanches for the purpose of risk management with regard to the Planpincieux glacier, located on the Italian side of Mont Blanc massif.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Since 2013, the Planpincieux glacier, has been studied to analyse the dynamics of ice collapses in a temperate glacier. Several documented ice avalanches and glacial floods (1929, 1952, 1982, 2005, 2017), which, in some cases, threatened the village of Planpincieux and damaged the municipal road, have been linked to this glacier. Starting from the summer of 2019, a fast moving ice volume, partially separated by the rest of the glacier tongue by a large crevasse, has drastically increased the occurrence of a new collapse with possible implications for the valley floor. Considering the potential risk, a glacier constant monitoring (GbInSAR) and an avalanche early warning system (avalanche Doppler radar) were deployed, and numerical modelling of ice avalanches from this glacier was made.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Thereby, we couple an empirical-statistical model with a physically-based mass flow model: (I) the rules of Alean (1985) for the angle of reach are fed into the software r.randomwalk in order to estimate worst-case reference travel distances for various scenarios of starting volumes, (II) the basal friction angle used in the physically-based tool r.avaflow is optimized against those reference travel distances for each volume scenario, (III) the travel distances and travel times are checked for plausibility against well-documented events, (IV) flow pressures and flow kinetic energies are computed with r.avaflow for each volume scenario.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The model results are well supported by empirical data for smaller events, whereas direct reference data for the larger scenarios are not available. Interpretation of the results further has to take into account that (A) for some scenarios, the empirical relationships had to be extended beyond their known range of validity, introducing additional uncertainty, and (B) the relationships do not work for snow-covered trajectories, that, for example, would decrease the friction and lead to longer travel distances. As a result, the outcomes can be, with some care, considered as worst-case assumptions for ice avalanches in summer, but are not valid for ice avalanches during the other seasons.&amp;lt;/p&amp;gt;</jats:p

Analysis of the Miage Glacier Lake GLOFs (Aosta Valley - Italy).

&amp;lt;p&amp;gt;Miage Glacier Lake is a glacial marginal lake that forms on the right snout of Miage Glacier, located in the Val Veny Valley (Aosta Valley &amp;amp;#8211; Italy). The lake has been experiencing seasonal drainages at least since the 1930&amp;amp;#8217;s and 15 events have been documented from 1930 to 1990. The lake position has been almost unvaried since the first existing maps of late 1700, but lake morphology experienced major changes after the drainage event of September 2004, after which the water level could not reach again a sufficient height to fill the 3 depressions that used to form a bigger lake until 2003 (36.000 m&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;). The lake having decreased its volume and surface, it did not seem by that time that GLOF from Miage Lake could cause any risk downstream (Deline et Al. 2004), but recent observation of Sentinel 2B satellite images &amp;amp;#160;led to the individuation of unusual lake expansion towards its north shore. Thus, an UAV survey was performed to assess the actual lake area in July 2019, and the integration of satellite images and UAV surveys demonstrated a consistent lake area expansion since 2015. Moreover an emptying occurred in late August 2019 so that another UAV survey could be performed, and water volume estimation could be performed by means of DEM differencing. An important water volume was individuated, reaching 196.000 m&amp;lt;sup&amp;gt;3&amp;lt;/sup&amp;gt; and an estimation of maximum subglacial GLOF debit has been performed. Global evolution trend of the glacier mass has been evaluated by analyzing different airborne Lidar surveys (1991-2008). A cumulated geodetic mass balance could be thus inferred and found good matching with remote sensed analysis (2003-2012) performed by means of stereo satellite imagery by Berthier et Al. in 2014. Average surface lowering of the glacier surface could be analyzed and average values of -1.12 m/yr could be observed around lake Miage. The strong elevation loss of Miage Glacier lower snout is probably the cause of the lowering of the piezometric level in intra-glacial water limiting maximum altitude that water level can reach in the lake, so that the bigger basin of 2004 cannot be filled anymore. Moreover, an analysis of recent GLOFs of Miage Lake gave an insight about the possible dynamics of lake subglacial drainage, suggesting the existence of 2 different mechanisms of emptying as some events occur with lower water debits, earlier in the season, and other events occur later in the summer season with major water debits. Similar GLOF behavior has been described at Plaine Morte Glacier Lake in the Canton of Bern-Switzerland (Fahrni 2018). Field surveys of 2018 showed very likely evidence of hydrostatic uplift of the ice dam, so multi temporal UAV surveys and GNSS field surveys are planned for 2020 to possibly highlight evidences of hydrostatic uplift of the glacier prior to GLOFs.&amp;lt;/p&amp;gt; </jats:p

Ice avalanche risk management from the Planpincieux glacier (Courmayeur - Italy)

&amp;lt;p&amp;gt;Instabilities occurring on temperate glaciers in the Alps have been the subject of several studies, which have highlighted preliminary conditions and possible precursory signs of break-off events.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Since 2013, the Planpincieux Glacier, located on the Italian side of Mont Blanc massif (Aosta Valley), has been studied to analyse the dynamics of ice collapses in a temperate glacier.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;These analyses have been conducted for several years, enabling the assessment of surface kinematics on the lower glacier portion and the different instability processes at the glacier terminus. During the period of the study, especially in the summer seasons, increases in velocities of the whole right side of the glacier tongue have been recorded. This fast sliding movement is mainly induced by water flow at the bottom of the glacier.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;In 2019 summer season, the increase of speed coincided with the opening of a large crevasse, which outlined a fast moving ice volume, assessed by photogrammetric techniques as 250.000 m&amp;lt;sup&amp;gt;3&amp;lt;/sup&amp;gt;.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;According to the risk scenarios, the collapse of this ice volume from the glacial body would have reached the valley floor, potentially affecting the access road to the Val Ferret valley.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Considering the potential risk, a civil protection plan has been deployed by the monitoring team of the Aosta Valley Autonomous Region, Fondazione Montagna sicura and CNR-IRPI.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Glacier displacements, variations in the glacier morphology and environmental variables, such as air temperature, rain and snowfall, have all been taken into account to implement the monitoring plan.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;This work outlines and summarises the steps used to develop the scientific knowledge into an integrated monitoring plan and a closure plan for the Val Ferret valley.&amp;lt;/p&amp;gt; </jats:p