Investigation and multi-scale monitoring of rockfall processes: Setup and preliminary results of the in-situ rock-slope laboratory at the Stubai Glacier, Tyrol (Austria)

Rockfalls are widespread processes in alpine landscapes, shaping landscape evolution while posing significant hazards to people and infrastructure. Rapid global warming leads to accelerated glacier retreat and permafrost degradation which alter the factors that predispose, trigger and control rock slope behavior, making it difficult to apply past experiences and knowledge to present-day conditions. In this context, a process-based understanding of geological, geomechanical and meteorological precursor factors that lead to slope instabilities is crucial. Specifically, continuous, multi-scale and multi-sensor observations are essential to understand predisposing factors and to characterize acceleration phases for estimating the timing of failures.

To address this challenge, we have established the in-situ rock-slope laboratory at the Schaufelspitze, Stubai Glacier (Tyrol, Austria), where rock slope instabilities at different scales are investigated using an integrated, multi-sensor monitoring setup. This location at an elevation between 2880 and 3332 m is an ideal test setting, combining recent rock slope activity with rapid deglaciation, evolving thermal regimes and changing meteorological intensities. The established and ongoing monitoring network combines in-situ temperature sensors and crackmeters with remote sensing techniques, including terrestrial laser scanning (TLS), unmanned aerial vehicle (UAV)-based thermal and photogrammetric surveys, ground-based interferometric synthetic aperture radar (GB-InSAR), time-lapse webcam photomonitoring , and meteorological data from nearby stations.

Preliminary results show that the designed remote sensing methods, complemented by in-situ sensors, allow to observe rock slope deformations across a wide range of both spatial and temporal scales. In this study, GB-InSAR shows more applicability to identify short-term accelerations and heterogeneous patterns that are difficult to capture with episodic surveys (e.g., with TLS or UAV). In addition, the use of thermal imaging adds information indicating surface temperature anomalies related to increased rock mass fracturing and loosening as well as water pathways and springs. In-situ temperature sensors capture spatial and temporal temperature variations, enabling the identification of potential rockfall activation areas.

The rock-slope laboratory aims therefore to establish a long-term record of acceleration and deformation phases of different processes and scales, as well as to identify predisposing and triggering mechanisms of specific conditions knowing the exact event timing. Particularly by integrating multiple sensors, it aims to identify robust, transferable triggers and possibly derive practical thresholds to support future early warning systems in high alpine environments. By combining remote sensing and in-situ data, this framework provides insights on slope processes in response to hydro-meteorological factors, which would be difficult to resolve using individual techniques.

Outputs will include: (i) the identification of different scaled rockfall processes in a high alpine setting; (ii) the characterization of rock slope instability drivers, acceleration phases and failure, and (iii) validated workflows for sensor setups and combinations, change detection and photomonitoring.