Multi-sensor monitoring and data integration reveal cyclical destabilization of the Äußeres Hochebenkar rock glacier

This study investigates rock glacier destabilization based on the results of a unique in situ and remote-sensing-based monitoring network focused on the kinematics of the rock glacier in Äußeres Hochebenkar (Austrian Alps). We consolidate, homogenize, and extend existing time series to generate a comprehensive dataset consisting of 14 digital surface models covering a 68-year time period, as well as in situ measurements of block displacement since the early 1950s. The digital surface models are derived from historical aerial imagery and, more recently, airborne and uncrewed-aerial-vehicle-based laser scanning (ALS and ULS, respectively). High-resolution 3D ALS and ULS point clouds are available at annual temporal resolution from 2017 to 2021. Additional terrestrial laser scanning data collected in bi-weekly intervals during the summer of 2019 are available from the rock glacier front. Using image correlation techniques, we derive velocity vectors from the digital surface models, thereby adding rock-glacier-wide spatial context to the point-scale block displacement measurements. Based on velocities, surface elevation changes, analyses of morphological features, and computations of the bulk creep factor and strain rates, we assess the combined datasets in terms of rock glacier destabilization. To additionally investigate potential rotational components of the movement of the destabilized section of the rock glacier, we integrate in situ data of block displacement with ULS point clouds and compute changes in the rotation angles of single blocks during recent years. The time series shows two cycles of destabilization in the lower section of the rock glacier. The first lasted from the early 1950s until the mid-1970s. The second began around 2017 after approximately 2 decades of more gradual acceleration and is currently ongoing. Both destabilization periods are characterized by high velocities and the development of morphological destabilization features on the rock glacier surface. Acceleration in the most recent years has been very pronounced, with velocities reaching 20–30 m a−1 in 2020–2021. These values are unprecedented in the time series and suggest highly destabilized conditions in the lower section of the rock glacier, which shows signs of translational and rotational landslide-like movement. Due to the length and granularity of the time series, the cyclic destabilization process at the Äußeres Hochebenkar rock glacier is well resolved in the dataset. Our study highlights the importance of interdisciplinary, long-term, and continuous high-resolution 3D monitoring to improve process understanding and model development related to rock glacier rheology and destabilization

RIVER MORPHOLOGY MONITORING OF A SMALL-SCALE ALPINE RIVERBED USING DRONE PHOTOGRAMMETRY AND LIDAR

An efficient alternative to labour-intensive terrestrial and costly airborne surveys is the use of small, inexpensive Unmanned Aerial Vehicles (UAVs) or Remotely Piloted Aerial Systems (RPAS). These low-altitude remote sensing platforms, commonly known as drones, can carry lightweight optical and LiDAR sensors. Even though UAV systems still have limited endurance, they can provide a flexible and relatively inexpensive monitoring solution for a limited area of interest. This study investigated the applicability of monitoring the morphology of a frequently changing glacial stream using high-resolution topographic surface models derived from low-altitude UAV-based photogrammetry and LiDAR. An understanding of river-channel morphology and its response to anthropogenic and natural disturbances is imperative for effective watershed management and conservation. We focus on the data acquisition, processing workflow and highlight identified challenges and shortcomings. Additionally, we demonstrate how LiDAR data acquisition simulations can help decide which laser scanning approach to use and help optimise data collection to ensure full coverage with desired level of detail. Lastly, we showcase a case study of 3D surface change analysis in an alpine stream environment with UAV-based photogrammetry. The datasets used in this study were collected as part of the ISPRS Summer School of Alpine Research, which will continue to add new data layers on a biyearly basis. This growing data repository is freely available for research

UAV-Photogrammetry, UAV laser scanning and terrestrial laser scanning point clouds of the inland dune in Sandhausen, Baden-Württemberg, Germany

This dataset contains unoccupied aerial vehicle (UAV)-based photogrammetric point clouds, orthophotos, UAV-borne laser scanning point clouds, and terrestrial laser scanning point clouds of three nature reserves of the Sandhausen inland dunes in Baden-Württemberg, Germany: Pflege Schönau, Pferdstrieb Süd, and Zugmantel-Bandholz. The three surveyed areas each have a size of about 10 ha. UAV-based photogrammetric data of the three sites were collected in February, September, and October 2021 with a ground sampling distance of 2.0 to 2.5 cm/px. UAV-borne laser scanning data were collected in August and September 2021 and resulting point clouds have pulse densities between 123 and 227 pts/m². Additionally, the site Zugmantel-Bandholz was surveyed with a terrestrial laser scanner in May 2022 using eight scan positions. GNSS measurements were recorded in-flight and/or taken on the ground and were tied into the SAPOS reference network (RTK/PPK) to georeference the data. This dataset captures the current state of the inland dune in 2021 and 2022, in particular the topography and vegetation cover in different seasons of the year

Terrestrial laser scanning data of the Äußeres Hochebenkar rock glacier close to Obergurgl, Austria acquired during the Innsbruck Summer School of Alpine Research

Permafrost phenomena like active rock glaciers are increasingly mapped and monitored with close range sensing techniques. Multi temporal and precise point clouds in high spatial resolution as they can be acquired by Terrestrial Laser Scanning (TLS), offer promising opportunities for detailed morphological analysis. Current research focuses on the quantification of morphological changes using objects moving with the surface of a creeping rock glacier. This data publication contains georeferenced (WGS 84 / UTM zone 32N; EPSG:32632) point clouds covering the tongue of the Äußeres Hochebenkar rock glacier located about 2 km south of Obergurgl. Point clouds were acquired using a TLS from different scan positions around the rock glacier during the Innsbruck Summer School of Alpine Research - "Close Range Sensing Techniques in Alpine Terrain"