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A rapid sequence of cascading events involving thermokarst lake outburst, local rock glacier front failure, debris flow development, and river blockage hit Radurschl Valley (Ötztal Alps, Tyrol) on 13 August 2019. Compounding effects from permafrost degradation and drainage network development within the rock glacier initiated the complex process chain. The debris flow dammed the main river of the valley, impounding a water volume of 120 000 m 3 that was partly drained by excavation to prevent a potentially catastrophic outburst flood. We present a systematic analysis of destabilizing factors to deduce the failure mechanism. The identification and evaluation of individual factors reveals a critical combination of topographical and sedimentological disposition, climate, and weather patterns driving the evolution of a thermokarst drainage network. Progressively changing groundwater flow and storage patterns within the frozen sediment accumulation governed the slope stability of the rock glacier front. Our results demonstrate the hazard potential of active rock glaciers due to their large amount of mobilizable sediment, dynamically changing internal structure, thermokarst lake development, and substantial water flow along a rapidly evolving channel network. [ABSTRACT FROM AUTHOR]

Multi‐temporal digital terrain models (DTMs) derived from airborne or uncrewed aerial vehicle (UAV)‐borne light detection and ranging (LiDAR) platforms are frequently used tools in geomorphic impact studies. Accurate estimation of mobilized sediments from multi‐temporal DTMs is indispensable for hazard assessment. To study volumetric changes in alpine environments it is crucial to identify and discuss different kind of error sources in multi‐temporal data. We subdivided errors into those caused by data acquisition, data processing, and spatial properties of the terrain. In terms of the quantification of surface changes, the propagation of errors can lead to high uncertainties. Three alpine catchments with different LiDAR point clouds of different origins (airborne laser scanning [ALS], UAV‐borne laser scanning [ULS]), varying point densities, accuracies and qualities were analysed, and used as basis for interpolating DTMs. The workflow was developed in the Schöttlbach area in Styria and later applied to further catchments in Austria. The main aim of the presented work is a comprehensive DTM uncertainty analysis specially designed for geomorphic impact studies, with a resulting uncertainty analysis serving as input for a change detection tool. Our findings reveal that geomorphic impact studies need the careful distinction between actual surface changes and different data uncertainties. ULS combines the benefits of terrestrial laser scanning with all the benefits of ALS. However, the use of ULS data does not necessarily improve the results of the analysis since the high level of detail is not always helpful in geomorphic impact studies. In order to make the different point clouds and DTMs comparable the quality of the ULS point cloud had to be reduced to fit the accuracy of the reference data (older ALS point clouds). Using a point cloud with a high point density with a regular planimetric point spacing and less data gaps, in the best case collected during leaf‐off conditions (e.g., cross‐flight strategy) turned out to be sufficient for our geomorphic research purposes. [ABSTRACT FROM AUTHOR]

A rapid sequence of cascading events involving thermokarst lake outburst, rock glacier front failure, debris flow development and river blockage hit Radurschl Valley (Ötztal Alps, Tyrol) on 13 August 2019. Compounding effects from multivariate permafrost degradation and drainage network development initiated the complex process chain. The debris flow dammed the main river of the valley, impounding a water volume of 120,000 m3 that was partly drained by excavation to prevent a potentially catastrophic outburst flood. Since the environmental forces inducing the debris flow evolved under ambiguous conditions, potentially destabilizing factors were analyzed systematically to deduce the failure mechanism and establish a basis for multi hazard assessment in similar settings. Identification and evaluation of individual factors revealed a critical combination of topographical and sedimentological disposition, climate, and weather patterns driving the evolution of thermokarst and debris flow. Progressively changing groundwater flow and storage patterns characterizing the hydraulic configuration within the frozen sediment accumulation governed the slope stability of the rock glacier front. The large amount of mobilizable sediment, dynamically changing internal structure, and substantial water flow along a rapidly evolving channel network eroded into the permafrost body, render active rock glaciers complex multi hazard elements in periglacial, mountainous environments. [ABSTRACT FROM AUTHOR]

Road networks are complex interconnected systems. Any sudden disruption can result in debilitating impacts on human life or the economy. Interruptions of the transport flow may lead to potentially severe consequences in terms of both direct and indirect losses. In particular, road systems in mountainous areas do not feature redundant elements at comparable economic efficiency. Therefore, assessment of network vulnerability is of major importance for guaranteeing the smooth functioning of societies, especially in those regions. Among various menacing hazards, landslides protrude as particularly destructive events jeopardizing the integrity of land transport systems by causing structural damage and network interruptions. The aim of this paper is to present how road infrastructure is vulnerable towards landslides events, with emphasis on the consequences for the affected road users. This is addressed on the Austrian region Vorarlberg, which allows cross-learning and cross-comparison of, for example, rural and urban areas, also at different scales. The focus of this case study is on resilience issues and support for decision making in the context of a large scale sectoral approach. By taking into account derivates of a high-resolution digital terrain model as well as geological properties, a landslide susceptibility map of the test region is derived by means of the weight of evidence method. This susceptibility map is concatenated with historic data of landslide inventories and a digital road graph in order to identify critical sections of the road network. Subsequently, effects of interruptions of the road network at these critical links are analyzed by applying a mesoscopic multi-agent transport simulation model. Results show the merits of using agent-based traffic modeling for assessing the impacts of road network interruptions on rural communities by providing insight into the characteristics of the population affected, as well as the effects on its daily routine in terms of detour costs. [ABSTRACT FROM AUTHOR]

Regions with marginal occurrence of discontinuous permafrost are very specific due their transition to non-permafrost conditions at recent times. Knowledge about the potential distribution of permafrost in the past and at present is crucial to understand its characteristics and dynamics as well as inherent processes. This analysis comprises the simulation of the potential distribution of discontinuous permafrost using six scenarios with different temperature depressions in the entire Reisseck Mountains (46°57'N, 13°22'E) for the year 2000 (Sc-2000), the Little Ice Age (Sc-LIA) and four scenarios for the Younger Dryas - locally referred to as Egesen - in the Alpine Lateglacial period (Sc-E1 to Sc-E4). The results were validated at two different spatial scales; at a regional scale for the entire study region Reisseck Mountains, Central Austria, with data from the distribution of relict and intact rock glaciers; at a local scale for the study area Hintereggengraben Valley - Hohe Leier with data from five years of continuous ground temperature monitoring using data from eight automatic miniature temperature dataloggers. Past conditions were simulated using the year 2000 as a basis for the lower limits of permafrost occurrence. A depression in the mean annual temperature of -1.4 K was used for modelling permafrost conditions during the LIA. Potential permafrost distribution in the Younger Dryas was modelled with temperature depression of -2.5 to -4.0 K compared to the LIA. Our results show a spatial distribution of 9.94 km² (3.1 %) in the sce- nario 2000 to 134.57 km² (42.1 %) in the scenario Sc-E4. The simulations of the thermal conditions in the Younger Dryas validated with the locations of the relict rock glacier suggest scenario Sc-E1 as the most probable. This implies a mean annual temperature depression of -2.5 K compared to LIA and depression of the lower limit of permafrost of ca. -560 m compared to the year 2000. A few relict rock glaciers are located in much lower areas and can therefore be stated as formed in pre-Egesen stages. As a further palaeoclimatical consequence we assume that all inactive rock glaciers in the Reisseck Mountains were still active in the LIA. [ABSTRACT FROM AUTHOR]

Valley glaciers in the European Alps are rapidly receding at present and in many cases show signs of glacier disintegration. This highly dynamical glacial-proglacial transition zone might include debris-covered ice bodies of various dimensions. In case of valley overdeepenings lakes form in the proglacial area related to glacier recession, glacier surface lowering or by melting of the debris-covered ice bodies in the proglacial area. Glacier surface lowering in combination with glacier recession cause the flooding of the glacier margin in the basin forming a glacier-lateral to supraglacial lake. We observed several large-scale ice-floating events between September 2016 and October 2018 at such a supraglacial lake adjacent to the largest glacier in Austria (Pasterze Glacier). The originally presumed proglacial lake seems to be rather a supraglacial lake covering large amounts of glacier ice, which steadily disintegrates forming icebergs. Multiple data were used to better understand the processes acting at this glacial-proglacial transition zone: Time-lapse camera images with a sub-daily temporal resolution (2016-2018) covering the area of interest give insight into acting processes. Differential GPS was used mapping the superficial glacier boundary for the period 2003-2018. Digital terrain models derived from terrestrial laser scanning (2010-2018) and unmanned aerial systems/UAS (2016-2018) as well as orthophotos also derived from UAS (2016-2018) were analysed to quantify lake and glacier extent as well as landform changes. Several ERT-profiles measured in the proglacial area between 2015 and 2018 (n=16) revealed massive ice lenses and extensive ice layers exceeding 20 m in thickness covered by different types of sediments. Automatic weather station and ground temperature data give further insight in the thermal characteristics of the area of interest. We conclude the following stages of process development at Pasterze Glacier: (a) rapid glacier recession into a basin overdeepend by the glacier; (b) glacial and glacio-fluvial sedimentation in the glacial-proglacial transition zone covering parts of the glacier or dead ice in the basin; (c) initial formation and enlargement of the glacier-lateral to supraglacial lake by steady melting and surface lowering of the glacier ice and debris-covered dead ice; (d) disintegration of glacier ice at the lake bottom or at the surface influenced by high water pressure along fractures showing signs of tilting, sudden disintegration and formation of icebergs; (e) steady melting of the floating icebergs accompanied by tilting events. The latter two stages are also relevant for tourists in the area because small-scale tsunami-like waves have been formed by such processes submerging the lake shore. [ABSTRACT FROM AUTHOR]

Assessment of both condition and reliability of engineering structures is essential for appropriate infrastructure maintenance. In particular, changes in geometry (i.e. deformation) are an essential feature of structural condition. Among recent developments of scanning methods that have opened up new possibilities for contactless and rapid measurement of structural geometry, methods based on satellite synthetic aperture radar (SAR) interferometry are especially suitable for precise surface deformation monitoring. By exploiting information contained in the phase values of co-registered, multi-temporal SAR imagery, ground deformation and corresponding displacement rates can be obtained with sub-centimetric precision.With the launches of Sentinel-1A and 1B in April 2014 and April 2016 respectively, C-band SAR data with a spatial resolution of 5×20 meters (Interferometric Wide Swath Mode) became freely available across large parts of the globe. The constellation of the two satellites entails a repetition time of 6 days, and resulting data are provided near-real time.Within the scope of a feasibility study, the general applicability of Sentinel-1 InSAR imagery for monitoring infrastructure assets is evaluated. Specifically, focus has been put on the assessment of the structural health of bridges in terms of deformation rates obtained by means of persistent scatterer interferometry (PSI). This differential interferometric SAR technique relies on strong reflecting objects that are constant over time, and can be used to obtain deformation time series and the deformation velocity estimated over the analysed permanent scatterer points.Bridge deformation monitoring tests are conducted at selected structures along the Austrian primary road network. Estimated permanent scatterer elevations are validated against in-situ measurements (ground truth). In addition, performance of Sentinel-1 based PSI is tested against ground-based measurements of the road geometry (i.e. changes in the longitudinal profile obtained via laserscanning) as well as UAV-based LiDAR measurements.Preliminary results confirm the general applicability of Sentinel-1 SAR data for bridge monitoring in Alpine terrain. At the same time, certain challenges related to selection of persistent scatterers, topographic phase correction as well as atmospheric correction still need to be overcome. [ABSTRACT FROM AUTHOR]

Based on the project ALPCHANGE researchers from both the University of Graz and Graz University of Technology established a permafrost monitoring network at five different monitoring areas in the Hohe Tauern National Park, Central Austria, in 2006. Methodically this network is primarily based on ground temperature measurements, geodetic surface velocity measurements of rock glaciers and surface change detection (e. g. rock fall) using terrestrial laser scanning. For the period 2013/14 the first report on these activities was delivered to the national park authorities indicating very permafrost-unfavourable conditions for the reporting year. Additionally, the paper discusses the concept for the documentation of gravitational processes which is going to be implemented in the next years. [ABSTRACT FROM AUTHOR]