Abstract
Glaciers are effective indicators of climate change and their constant loss in size and volume, is considered an undoubtable sign of global warming. Glacier shrinkage is worsening the geotechnical and mechanical properties of rocks in high mountain areas consequently affecting the slope stability and increasing risks for both alpinists and society at large. A high number of phenomena is consequence of the paraglacial dynamics whose intensity is directly linked to the rate of glacier melting and debuttressing. Within this context it is necessary to increase knowledge of the areas most subjected to slope instabilities to understand their predisposing conditions, the relationship with glacier melt and the effect they can exert on alpine paths and infrastructures. By means of orthophotos, Digital Elevation Models (DEM) and satellite data we investigated the glaciers of the Venosta Valley in South Tyrol. Firstly we focused on their evolution between 1997 and 2020. The outlines for the years 1997, 2005 and 2017 were retrieved from the official South Tyrol data portal, for the year 2020 we manually digitized all the glaciers on an updated orthophoto provided by the Bolzano Province and with InSAR data to detect debris covered portions of glaciers. Then we focused on the paraglacial events that discharged debris over glaciers. We manually digitized all the slope instability events, creating an inventory of the high altitude glacial related instabilities. These events were detected and analysed with orthophotos, DEMs and Google Earth 3D viewer of the last decades data. This study highlights that between 1997 and 2020 these glaciers suffered a strong area contraction (-38% in the Ortles-Cevedale group and -38.9% in the Ötztal group) and in these sectors it is possible to count a total of 500 instability events. With this research we investigated, for the study areas, the relationship between topography, glacier regression and slope instabilities providing insights to further investigate the connection between climate change and paraglacial dynamics in alpine regions. The slope instability inventory allowed us to compute statistics of rockfall main parameters in order to identify particularly vulnerable areas and evaluate the exposition of high alpine paths to climate related hazards.