Exploiting InSAR and multi-source data to study periglacial environments in the Alps at different space and time scales
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The slope instability in alpine areas is a phenomenon related to superficial landslides, deep-seated gravitational slope deformations and permafrost creep. The systematic monitoring of changes over time caused by the slope movements is of high importance for a proactive management of natural hazards related to these phenomena. Moreover, since permafrost is sensitive to the changing in climate conditions, observing its dynamics is a key issue in alpine environments. Rock glaciers, which are the most common geomorphological evidence of permafrost in alpine regions, are characterized by creeping processes that generate a downstream displacement with speed rates ranging from a few cm to more than 1 meter per year. This displacement varies from year to year and seasonally. The three-years project ALPSMOTION (ALPine Slow slope Movement moniTorIng and detectiON with remote and proximal sensing) project started in August 2016 aims at combining and assimilating different approaches to detect slow movements in alpine regions using in situ and remote sensing data. To this end, the area of Lazaun located in Schnalstal/Val Senales (South Tyrol, Italy) has been selected as test area. Lazaun includes an active rock glacier and a complete set of glacial and periglacial landforms. The kinematic behaviour of Lazaun rock glacier is still poorly investigated, and the various techniques comprised by the project will be tested on it in order to fully understand its dynamics in relation to climate. The project activities will consider the following data sets: Sentinel-1, COSMO SkyMed and TerraSAR-XSAR (Synthetic Aperture Radar), GB-SAR (Ground Based SAR), GPS (Global Positioning System), UAV (Unmanned Aerial Vehicles) and TLS (Terrestrial Laser Scanner). These data will be exploited in order to analyse the permafrost deformation at different temporal and spatial scales. One of the core techniques used in this project is the InSAR. InSAR can measure the surface displacement of vegetation- and snow-free areas with a millimetric accuracy. In addition, the space-born InSAR is capable to acquire data over very large areas with high repetition frequency (up to a few days). These characteristics, will allow both the estimation of the Lazaun rock glacier displacement rate and the detection of the activity status of the rock glaciers over the entire South Tyrol updating the regional rock glacier inventory. In particular, the second activity will enable to distinguish active and inactive landforms based on a kinematic criterion using an automatic and cost-effective methodology. It is worth noting that, the accuracy of satellite-based derived products will be assessed over the Lazaun test area exploiting the ground based data collected over the area (e.g., GPS and GB-SAR data). Additionally, space-born InSAR is potentially capable to detect short-term displacement variations due to their high repetition frequency e.g. less than 5 days for COSMO SkyMed and 6 days for Sentinel-1. These are among the most promising results since the short-term rock glacier dynamics, such as the seasonal and infra-seasonal rhythms, is still poorly known and difficult to be systematically monitored using ground-based techniques. In this work we present and discuss the first results obtained with the project and the approaches used to combine data coming from different sources over different time and space scales.