Publikationen ¶

Electrical resistivity tomography (ERT) is widely used to map, characterize, and monitor the ground in alpine and periglacial environments, where coarse blocky surfaces are often ubiquitous. ERT measurements typically use conventional steel electrodes in combination with a water-soaked sponge. However, ensuring an optimum contact resistance between the electrodes and the ground to obtain high-quality data is often challenging and requires considerable logistical, physical, and time commitment. To overcome this, we tested a promising sand-filled, fist-sized conductive textile electrode. We conducted ERT measurements using both steel and textile electrodes at a landslide and two rock glaciers in the European Alps with coarse blocky surfaces and performed statistical analyses to test the accuracy and precision of the proposed textile electrodes. Our results show that the textile electrodes can be used as an alternative to the conventional steel electrodes without limitations, as they ensure good galvanic contact with the ground and accurate resistivity measurements. The use of textile electrodes also resulted in lower contact resistances, less time invested, physical and logistical advantages, and reduced risk of injury. In the future, this will enable applications such as enhanced ERT monitoring and/or faster (quasi-3D) imaging of the interior of entire landforms.

• La part de forêts protectrices avec peu de régénération a encore augmenté durant la dernière décennie du fait de leur densification et d'un abroutissement
toujours intense des ongulés.
• Selon l'Inventaire forestier national (IFN), 44 % des forêts suisses sont des forêts protectrices. Elles protègent la population et les infrastructures contre les dangers naturels tels que glissements de terrain, avalanches, chutes de pierres ou laves torrentielles.
• Par endroits, les perturbations accrues causées par les changements climatiques affaibliront leur effet protecteur. Pour limiter au maximum leur impact, la résilience de ces forêts doit être augmentée.

• In der letzten Dekade hat der Anteil des Schutzwaldes mit wenig Verjüngung erneut zugenommen, weil die Schutzwälder dichter geworden sind und der Verbiss durch Schalenwild auf hohem Niveau verharrte.
• 44 % des Schweizer Waldes sind gemäss Landesforstinventar Schutzwald. Er schützt Menschen und Sachwerte vor Naturgefahren wie Rutschungen, Lawinen, Steinschlag oder Murgängen.
• Die zunehmenden Störungen aufgrund des Klimawandels werden die Schutzwirkung des Waldes gebietsweise mindern. Um solche Beeinträchtigungen möglichst gering zu halten, muss die Resilienz der Schutzwälder erhöht werden.

This study investigates the runout and depositional behavior of the Tangni debris flow in the Garhwal Himalaya, India, through a series of controlled experiments conducted at the newly developed facility at CSIR-Central Building Research Institute, Roorkee. The experiments focused on evaluating the influence of water content, initial volume, and grain size distribution on debris flow dynamics. Debris flow experiments reveal that small changes in water content can trigger abrupt transitions in flow regimes, significantly altering runout distances and deposition patterns. Additionally, dimensionless parameters were calculated to characterize flow regimes, and granulometric analysis was performed on the deposited material. The results show that runout distance and deposition area increase with higher water content and larger initial volumes, whereas finer content reduces runout. Granulometric analysis revealed a clear segregation of coarse particles, with enrichment at the margins and towards the flow front, indicating that coarse particles enhance the destructive potential of debris flows. Dimensionless analysis identified the experimental flows as predominantly frictional in nature. The findings demonstrate consistency with natural debris flows and align with global experimental studies, providing valuable insights into the behavior of debris flows in the Indian Himalayas. Despite limitations due to scaling effects and reconstruction challenges, this study highlights the importance of experimental approaches in advancing our understanding of debris flows, particularly in regions lacking extensive historical data and monitoring infrastructure.

The Indian Himalayan region is the origin of numerous natural hazards, including landslides, earthquakes, floods, cloudbursts, etc. (Dash et al. 2021; Falae et al. 2021; Kanungo and Sharma 2014). Uttarakhand, located in the northwest Indian Himalayas, is one of the most landslide-prone states in India. In a recently published report by the National Remote Sensing Centre (NRSC) India, all the 13 districts of Uttarakhand state are severely affected by landslides and the Chamoli district ranks 3 among 13 districts of Uttarakhand and ranks 19 among 147 landslide-prone districts in the country according to the landslide density (Jain et al. 2023). Over the past three decades, Chamoli has experienced several destructive mass movement events, including the 2013 Kedarnath tragedy, the Chamoli rock and ice avalanche on February 7, 2021, land subsidence in Joshimath during 2023, etc. In 1999, Chamoli was struck by an earthquake with a magnitude of 6.8 on the Richter scale, with its epicenter near Gopeswar township. In addition to landslides and earthquakes, Chamoli has also faced numerous disasters caused by cloudbursts and flash floods. National Highway 58 connects Uttarakhand with the rest of the country, entering Chamoli district through Karnaprayag and extending to Badrinath. This highway passes through the Alakananda Valley, traversing many landslide-prone zones. In a recent study, Ramiz et al. (2023) found that about 27% of the areas along the highway corridor from Rishikesh to Badrinath is highly susceptible to landslides. Frequent landslides, including debris flows, rockfalls, debris slides, and subsidence, disrupt traffic and deposit materials in the river, increasing the likelihood of river damming (Dash et al. 2022, 2023) and traffic disruption. A similar traffic disruption occurred due to a rock avalanche near Patalganga Langsi Tunnel on the Badrinath Highway of Chamoli district on July 10, 2024. This is an area known for frequent rockfall, and debris slide events, as noted by earlier researchers.

Glide avalanches present a significant and repetitive challenge to many operational forecasting programs, and they are likely to become more frequent. While the spatial location of glide release areas is extremely consistent, the onset of glide avalanche release is notoriously difficult to forecast, and their destructive potential can be immense. Thus, the timing and dynamics of glide avalanches is an important area of study. To better understand these processes, and to improve assessments of risk to transportation corridors and infrastructure, event documentation is key. Here, we survey a large glide avalanche event along the Going-to-the-Sun Road in Glacier National Park, Montana, USA, during road opening operations in the spring of 2022. Using three sets of terrestrial lidar data (pre-event, post-event, and snow-off), we quantified key aspects of the avalanche and created powerful visualizations for analysis. Further, we evaluated meteorological data from automated weather stations between the onset of glide cracking and avalanche release. Last, we synthesized lidar data with a numerical dynamics model to replicate the event in a simulated environment. Using the tuned model, we determined the critical mean snow depth in the release area necessary for an avalanche to reach the road (4.2 m). Our method may be of particular use for glide avalanches, which tend to release in roughly the same place and time each year at a known interface. This could make the calculated critical depths more consistently reliable and preclude the need for additional tuning in dynamics models. As 1) lidar technology continues to improve and reduce in cost, 2) transportation corridors continue to extend into avalanche terrain, and 3) glide avalanches potentially become increasingly frequent, the synthesis outlined here provides a valuable tool for operational forecasters considering infrastructure threatened by glide events.

Mixed species can increase the stability of forest ecosystems against disturbances. However, the benefits of mixing cannot be generalized for all forest types and tree species combinations. To investigate the role of tree species composition in the responses of tree growth to late frost and drought, we constructed tree-ring series from forest stands with varying abundances of silver fir (Abies alba) and Turkey oak (Quercus cerris) at two sites in southern Italy. We studied (i) intra- and interspecific responses to late frost and drought stress, (ii) impact of tree species composition on these responses, and (iii) relationships between tree growth and climatic and structural variables. In the drier region, both species were more resistant to drought than to late frost. Moreover, Turkey oak was less resistant than silver fir to late frost in drier site conditions but showed greater resistance in wetter ones. The impact of tree species composition on plot-level responses was observed for drought resilience components at the drier site. Additionally, plot diameter heterogeneity positively influenced growth resistance to both stressors, while basal area negatively affected drought resistance. Water balance played a central role in the growth of both species, but silver fir growing in drier conditions was less influenced than silver fir growing in wetter ones. Silver fir can adapt growth strategies to deal with different environmental settings. This study shows that lower stand density (basal area: 41–83 m²/ha in this study) and greater structural heterogeneity (Gini index: 0.1–0.4) contribute to greater stand-level resilience in Mediterranean forests.

Rock slope instabilities and failures from permafrost rocks are among the most significant alpine hazards in a changing climate and represent considerable threats to high-alpine infrastructure. While permafrost degradation is commonly attributed to rising air temperature and slow thermal heat propagation in rocks, the profound impact of water flow in bedrock permafrost on warming processes is increasingly recognised. However, quantifying the role of water flow remains challenging, primarily due to the complexities associated with direct observation and the transient nature of water dynamics in rock slope systems. To overcome the lack of a quantitative assessment, we combine datasets of rock temperature measured in two deep boreholes (2016–2023), with electrical resistivity tomography measurements repeated monthly in 2013 and 2023; the site-specific temperature–resistivity relation determined in the laboratory with samples from the study area; and borehole piezometer data. Field measurements were carried out at the permafrost-affected north flank of the Kitzsteinhorn (Hohe Tauern range, Austria), which is characterised by significant water outflow from open fractures during the melt season. Borehole temperature data demonstrate a seasonal maximum of the permafrost active layer of 4–5 m. They further show abrupt temperature changes (∼ 0.2–0.7 °C) at 2, 3, and 5 m depth during periods with enhanced water flow and temperature regime changes between 2016–2019 and 2020–2022 at 10 and 15 m depth, which cannot be explained solely by conductive heat transfer. Electrical resistivity measurements repeated monthly reveal a massive decrease in resistivity from June to July and the initiation of a low-resistivity (< 4 kΩ m) zone in the lower part of the rock slope in June, gradually expanding to higher rock slope sections until September. We hypothesise that the reduction in electrical resistivity of more than an order of magnitude, which coincides with abrupt changes in borehole temperature and periods of high water heads up to 11.8 m, provides certain evidence of snowmelt water infiltration into the rockwall becoming pressurised within a widespread fracture network during the thawing season. This study shows that, in addition to slow thermal heat conduction, permafrost rocks are subjected to sudden push-like warming events and long-lasting rock temperature regime changes, favouring accelerated bottom-up permafrost degradation and contributing to the build-up of hydrostatic pressure, potentially leading to slope instability.

The influence of climate change on snow avalanches, particularly for the end of this century, remains uncertain, underscoring the need for further research. To assess the possible consequences of potential changes in snow accumulation and temperature and their impact on avalanche hazard, we introduce a comprehensive multi-step framework. It includes the analysis of climate change scenarios as well as the modeling of future snow covers and the simulation of avalanches in a case study region in central Switzerland.
Using a downscaling and a quantile mapping approach, we considered the high emission RCP8.5 from the CH2018 Swiss climate change scenarios and simulated a potential snow cover of more than 100 future winters with the snow cover model SNOWPACK. Changing snow accumulation and snow cover temperature was taken into account for two future time frames. The changed parameters were used in the RAMMS::EXTENDED avalanche simulation software on large scale.
The results indicate that changes in snow accumulation and temperature have a considerable impact on the run-out of avalanches. The results strongly depend on the climate model, without a clear overall trend in snow accumulation across the selected model chains. Snow accumulation and layer temperature can increase or decrease. However, for snow cover temperature, an increase in the mean snow temperature, especially towards the end of the century, can be expected. In future scenarios with reduced snow accumulation and rising temperatures, avalanche simulations show a decrease in the affected area.
The workflow from climate scenario analysis to avalanche hazard modeling serves as an initial method for estimating future avalanche extents in the context of climate change on a large scale and can be useful for achieving future protection and adaptation goals.

Recent studies have brought to light large amounts of evidence for enhanced rock slope failure from degrading permafrost rock walls. These failures have previously been thought to be subaerial and triggered by thermal heat propagation from rising air temperatures into the exposed rock faces. However, we have neglected the fact that the dividing line between cold and warm basal states of polythermal glaciers has shifted some hundreds of meters upwards at the same time. This means that previously frozen and ice-filled fragmented rock walls under cold glaciers have suddenly and for the first time in thousands of years been exposed to (i) hydrostatic pressures, (ii) warming and degrading ice in fractures, and (iii) rock mechanical degradation in warming rocks. In this paper, we hypothesize that the transition from cold- to warm-based glaciers, a scarcely observed but widespread phenomenon, caused the massive rock slide. To challenge this hypothesis, we investigated the 3.9 to 4.3×10⁶ m³ rock slide at Bliggspitze on 29 June 2007, which detached from a north-exposed, glacier-covered rock slope at 3200 m above sea level. We (a) have analyzed the glacier transition since 1971 using aerial photographs coincident to meteorological data; (b) compared 2013–2016 ground surface temperature measurements to infer permafrost-prone and cold glacier thermal conditions; (c) categorized springs mapped in summer 2001/2012 according to geomorphological features and mineralization; (d) performed electrical resistivity tomography subsequent to failure on the destabilized rock flank in 2009; (e) conducted rock testing in frozen and unfrozen conditions; and (f) modeled the mechanical impact of hydrostatic pressure, degradation of permafrost, and glacier retreat in a universal distinct element code (UDEC). Aerial photos indicate the existence of a cold glacier from 1971–2003 above the failure volume. On the rock face above the failure volume, ground surface temperature measurements demonstrate permafrost-favorable conditions and underpin the presence of former and present cold-based glacier compartments. Since 2003, the warming of the Northern Bliggferner Glacier has been evident in the lower and upper parts. In 2007, subsequent to the warmest January–June period in a 228-year temperature record in the area of Bliggspitze, the glacier opened massive ice crevasses above the later rock slide, causing frequent ice fall. New springs developed in the former permafrost flank, and some were strong enough to cause debris flows. The high mineralization measured at springs at a proximal distance to the failure volume indicates active-layer thaw. The inversion of electrical resistivity tomography revealed thaw that reached several decameters in depth in the collapsed rock mass 2 years after failure. The tensile strength of tested paragneiss rock samples decreased by −40 % from frozen to unfrozen states, which reflects the mechanical degradation of rock bridges under warming permafrost. In this paper, we demonstrate a new type of rock slope failure mechanism triggered by the uplift of the cold–warm dividing line in polythermal alpine glaciers, a widespread and currently under-explored phenomenon in alpine environments worldwide.