[{"pid":"wsl:34019","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:34019","citation":{"WSL":"Baumer J., Metzger N., Hafner E.D., Caye Daudt R., Wegner J.D., Schindler K. (2023) Automatic image compositing and snow segmentation for alpine snow cover monitoring In Swiss conference on data science (SDS). 2023 10th IEEE Swiss conference on data science (SDS). Piscataway: IEEE. 77-84. https://doi.org/10.1109/SDS57534.2023.00018"},"doi":"10.1109/SDS57534.2023.00018","abstract":"Accurate snow cover maps are an important tool in a large variety of applications including avalanche research. The WSL Institute for Snow and Avalanche Research (SLF) has developed a snow cover mapping system for the Dischma valley in Davos, based on ground-based cameras. Their goal has been to validate snow-cover maps derived from satellite data. In the currently implemented system, several steps require manual work. The goal of this paper is to automate SLF's approach by applying a deep learning framework. For the training of our models, we have access to data from multiple cameras mounted in the Dischma valley. In our approach, we first apply deep learning to perform fog classification and then to do pixel-wise snow segmentation. Unlike the current procedure our method is independent of image- and camera-specific thresholds. In our experiments, we compare a model that is trained on images from all cameras to camera-specific models for both tasks. For the fog classification, we aim for a higher recall to be able to detect most of the foggy images. We show that, when tuned to achieve the same precision as the baseline, our model improves recall by 17%. For the snow segmentation, we evaluate our models based on the Fl-score. When using our fully automated machine learning model without any manually selected thresholds, we achieve a higher Fl-score only for a part of the cameras in the valley, and on average, this comes at a cost of 2.3%. We also show that for the case of a new camera being mounted in the Dischma valley, our models for both tasks can still be used for that new camera and will achieve similar results compared to the currently mounted cameras."},{"pid":"wsl:34704","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:34704","citation":{"WSL":"Bebi P., Allgaier Leuch B., Bugmann H., Conedera M., Frehner M., Insinna P., … Zürcher S. (2023) Wildhuftiere und Waldverjüngung: Wenn die Zeit davonläuft Schweiz. Z. Forstwes. 174(5), 274-279. https://doi.org/10.3188/szf.2023.0274"},"doi":"10.3188/szf.2023.0274","abstract":"Der rasch fortschreitende Klimawandel gefährdet wichtige Waldleistungen, da sich die Wälder den sich verändernden Bedingungen nicht schnell genug anpassen können. Damit die Waldleistungen auch in Zukunft erbracht werden können, ist eine möglichst artenreiche Verjüngung zukunftsfähiger Baumarten zentral. So werden die Wälder gegenüber Störungen resilienter. Der in vielen Regionen der Schweiz seit Jahrzehnten sehr hohe Verbiss der Waldverjüngung durch Wildhuftiere stellt in dieser Hinsicht eine grosse Herausforderung dar. Verschiedene Beispiele zeigen, dass eine ausreichende Waldverjüngung nur möglich ist, wenn nebst waldbaulichen Massnahmen eine gezielte, regional differenzierte Reduktion des heutigen Wildbestandes erfolgt. Dies wiederum erfordert eine konstruktive und auf gemeinsamen Zielen beruhende Zusammenarbeit zwischen Jagd und Forst sowie gesellschaftlich-politische Rahmenbedingungen, die diese Zusammenarbeit im Sinn des nationalen Gesetzesauftrags und der Erfüllung der zukünftigen Aufgaben des Waldes fördern und wertschätzen."},{"pid":"wsl:34980","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:34980","citation":{"WSL":"Berger C., Zimmermann F., Mauerhofer R., Christen M. (2023) MurGame: Protect your village from debris flows! In M. Pirulli, A. Leonardi, & F. Vagnon (Eds.), E3S web of conferences: Vol. 415. 8th international conference on debris flow hazard mitigation (DFHM8). Les Ulis Cedex A: EDP Sciences. 07002 (4 pp.). https://doi.org/10.1051/e3sconf/202341507002"},"doi":"10.1051/e3sconf/202341507002","abstract":"Past debris flow events, like in Bondo (2017) and Brienz (2005) in Switzerland have been heavily covered in the (Swiss) media, illustrating how destructive such events can get. Protection measures play an important role in dealing with natural hazards. Debris flows are considered to be very rare, complex and multidimensional processes. Imagining and foreseeing the course and progression of a debris flow as well as estimating the potential damage and the influence of protection measures is a difficult task. Serious games offer a possibility to simulate these kinds of situations. With the MurGame, we have developed an application for natural hazard prevention. In the three-dimensional, interactive game, a village is created by selecting different objects, such as residential buildings or schools. Debris flow simulations show, which buildings would be destroyed and what damage would occur in the event of a debris flow. Different protection measures can be implemented to protect the village and their effectiveness can be monitored during the simulations. After the event, it is necessary to evaluate which measures offer the desired protection, what they may cost and how the needs of the population are met. The MurGame can be played online at www.murgame.ch."},{"pid":"wsl:32728","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:32728","citation":{"WSL":"Bergfeld B., Van Herwijnen A., Bobillier G., Rosendahl P.L., Weißgraeber P., Adam V., … Schweizer J. (2023) Temporal evolution of crack propagation characteristics in a weak snowpack layer: conditions of crack arrest and sustained propagation Nat. Hazards Earth Syst. Sci. 23(1), 293-315. https://doi.org/10.5194/nhess-23-293-2023"},"doi":"10.5194/nhess-23-293-2023","abstract":"For a slab avalanche to release, we need sustained crack propagation in a weak snow layer beneath a cohesive snow slab – a process we call dynamic crack propagation. Field measurements on crack propagation are very scarce. We therefore performed a series of crack propagation experiments, up to 9 m long, over a period of 10 weeks and analysed these using digital image correlation techniques. We derived the elastic modulus of the slab (0.5 to 50 MPa), the elastic modulus of the weak layer (50 kPa to 1 MPa) and the specific fracture energy of the weak layer (0.1 to 1.5 J m⁻²) with a homogeneous and a layered-slab model. During crack propagation, we measured crack speed, touchdown distance, and the energy dissipation due to compaction and dynamic fracture (5 mJ m⁻² to 0.43 J m⁻²). Crack speeds were highest for experiments resulting in full propagation, and crack arrest lengths were always shorter than touchdown lengths. Based on these findings, an index for self-sustained crack propagation is proposed. Our data set provides unique insight and valuable data to validate models."},{"pid":"wsl:33118","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:33118","citation":{"WSL":"Blatny L., Löwe H., Gaume J. (2023) Microstructural controls on the plastic consolidation of porous brittle solids Acta Mater. 250, 118861 (14 pp.). https://doi.org/10.1016/j.actamat.2023.118861"},"doi":"10.1016/j.actamat.2023.118861","abstract":"Through stochastic-numerical microstructure-based experiments, the plastic consolidation under compression of porous brittle solids, with porosities from 0.25 to 0.75 and a large variety of microstructural characteristics, has been investigated. This was made possible by generating microstructures from Gaussian random fields in order to obtain stochastic ensembles of structures with prescribed properties, which are then simulated within the material point method. Below a critical imposed strain rate, the consolidation behavior is found to be very weakly affected by the degree of heterogeneity and anisotropy. Structures where the solid phase takes up more space than the void phase have a consolidation response approximately independent of the structural geometry and dimensionality (comparing two- and three-dimensional structures). Finally, we show that the consolidation of two-dimensional structures collapses on a single master curve that can be described by a simple function similar to one presented for a completely different system, namely a system of interacting discrete cohesive disks. In this function, we report a universal parameter largely independent of material specifications."},{"pid":"wsl:33662","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:33662","citation":{"WSL":"Borner J., Bartelt P. (2023) Calculating impact pressures in numerical avalanche and rockfall models In L. Zdravkovic, S. Kontoe, D. M. G. Taborda, & A. Tsiampousi (Eds.), Proceedings 10th NUMGE 2023. 10th European conference on numerical methods in geotechnical engineering. sine loco: International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE). (6 pp.). https://doi.org/10.53243/NUMGE2023-370"},"doi":"10.53243/NUMGE2023-370","abstract":"Calculating contact/impact pressures with numerical finite element software remains a difficult task. It is especially difficult for highly compactable, plastic materials where the elastic fraction of the strain is very small. This is the case in most impact problems in natural hazards. One example is the impact of rockfall dams by large, rotating rocks. Another is the impact of pylons, walls and other obstacles by snow avalanches. We embed work-energy methods within numerical avalanche and rockfall models to make the calculation of impact pressures in natural hazards more applicable for engineering practice. Firstly, we can greatly reduce the computation time and secondly, the input parameters are much more intuitive for practitioners due to the use of purely plastic compactive material behaviour."},{"pid":"wsl:33072","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:33072","citation":{"WSL":"Bühler Y., Stoffel A., Eberhard L., Bührle L. (2023) Fotogrammetrische Schneehöhenkartierung aus Drohnen-, Flugzeug- und Satellitenbildern In Eidg. Forschungsanstalt für Wald, Schnee und Landschaft, WSL (Ed.), WSL Berichte: Vol. 134. Neue Fernerkundungstechnologien für die Umweltforschung und Praxis. Birmensdorf: Eidg. Forschungsanstalt für Wald, Schnee und Landschaft, WSL. 61-66. https://doi.org/10.55419/wsl:33072"},"doi":"10.55419/wsl:33072","abstract":"Die räumliche Variabilität der Schneedecke im Gebirge wird durch eine komplexe Kombination topographischer und meteorologischer Faktoren beeinflusst. Innerhalb weniger Meter Distanz finden sich schneefreie Stellen, aber auch Mulden mit Schneehöhen von mehreren Metern. Dies hat grosse Auswirkungen auf die Lawinengefahr, die Wasserspeicherkapazität der Schneedecke sowie Flora und Fauna im Gebirge. Meist wird die Schneehöhe im Gebirge mit Punktmessungen an Wetterstationen oder von Hand erfasst. Allerdings können solche Messungen nur ein unvollständiges Bild der tatsächlichen Schneeverteilung zeichnen. Mit neuen Fernerkundungsplattformen wie Drohnen, Flugzeugen oder optischen Satelliten können photogrammetrisch sehr präzise Oberflächenmodelle erstellt werden. Subtrahiert man ein Oberflächenmodell ohne Schneebedeckung von einem Oberflächenmodell mit Schneebedeckung, erhält man eine räumlich zusammenhängende Kartierung der Schneehöhenverteilung. Am SLF werden seit 2010 solche präzisen Schneehöhenkarten erstellt. Diese erweisen sich als wichtige Grundlage für zahlreiche Anwendungen.

The spatial variability of the mountain snowpack is influenced by a complex combination of topographical and meteorological factors. Within a few meters there are snow-free spots, but also hollows with snow depths of several meters. This has a major impact on the risk of avalanches, the water storage capacity of the snowpack and the flora and fauna in the mountains. The snow depth in the mountains is usually recorded with point measurements at weather stations or by hand. However, such measurements can only paint an incomplete picture of the actual snow distribution. With new remote sensing platforms such as drones, airplanes or optical satellites, very precise surface models can be created photogrammetrically. Subtracting a surface model without snow cover from a surface model with snow cover results in a spatially coherent mapping of the snow depth distribution. Such precise snow depth maps have been created at the SLF since 2010. These prove to be an important basis for numerous applications."},{"pid":"wsl:34217","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:34217","citation":{"WSL":"Bührle L.J., Marty M., Eberhard L.A., Stoffel A., Hafner E.D., Bühler Y. (2023) Spatially continuous snow depth mapping by aeroplane photogrammetry for annual peak of winter from 2017 to 2021 in open areas Cryosphere 17(8), 3383-3408. https://doi.org/10.5194/tc-17-3383-2023"},"doi":"10.5194/tc-17-3383-2023","abstract":"Information on snow depth and its spatial distribution is important for numerous applications, including natural hazard management, snow water equivalent estimation for hydropower, the study of the distribution and evolution of flora and fauna, and the validation of snow hydrological models. Due to its heterogeneity and complexity, specific remote sensing tools are required to accurately map the snow depth distribution in Alpine terrain. To cover large areas (>100 km²), airborne laser scanning (ALS) or aerial photogrammetry with large-format cameras is needed. While both systems require piloted aircraft for data acquisition, ALS is typically more expensive than photogrammetry but yields better results in forested terrain. While photogrammetry is slightly cheaper, it is limited due to its dependency on favourable acquisition conditions (weather, light conditions). In this study, we present photogrammetrically processed high-spatial-resolution (0.5 m) annual snow depth maps, recorded during the peak of winter over a 5-year period under different acquisition conditions over a study area around Davos, Switzerland. Compared to previously carried out studies, using the Vexcel UltraCam Eagle Mark 3 (M3) sensor improves the average ground sampling distance to 0.1 m at similar flight altitudes above ground. This allows for very detailed snow depth maps in open areas, calculated by subtracting a snow-off digital terrain model (DTM, acquired with ALS) from the snow-on digital surface models (DSMs) processed from the airborne imagery. Despite challenging acquisition conditions during the recording of the UltraCam images (clouds, shaded areas and fresh snow), 99 % of unforested areas were successfully photogrammetrically reconstructed. We applied masks (high vegetation, settlements, water, glaciers) to increase the reliability of the snow depth calculations. An extensive accuracy assessment was carried out using check points, the comparison to DSMs derived from unpiloted aerial systems and the comparison of snow-free DSM pixels to the ALS DTM. The results show a root mean square error of approximately 0.25 m for the UltraCam X and 0.15 m for the successor, the UltraCam Eagle M3. We developed a consistent and reliable photogrammetric workflow for accurate snow depth distribution mapping over large regions, capable of analysing snow distribution in complex terrain. This enables more detailed investigations on seasonal snow dynamics and can be used for numerous applications related to snow depth distribution, as well as serving as a ground reference for new modelling approaches and satellite-based snow depth mapping."},{"pid":"wsl:34726","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:34726","citation":{"WSL":"Bürli S., Ensslin A., Kempel A., Fischer M. (2023) Are rare plant species less resistant than common ones to herbivores? A multi-plant species study using above- and below-ground generalist herbivores Ecol. Evol. 13(9), e10482 (21 pp.). https://doi.org/10.1002/ece3.10482"},"doi":"10.1002/ece3.10482","abstract":"Rare plant species are suggested to be less resistant to herbivores than common species. Their lower apparency and the fact that they often live in isolated populations, resulting in fewer herbivore encounters, might have led to the evolution of reduced defences. Moreover, their frequent lower levels of genetic diversity compared with common species could negatively affect their resistance against enemies. However, the hypothesis that plant resistance depends on plant regional and local rarity, independently of habitat and competitive and growth strategy, lacks evidence. To test this hypothesis, we assessed the performance and preference of one belowground and three aboveground generalist invertebrate herbivores from different taxonomic groups as indicators of plant resistance. Herbivores were fed a total of 62 regionally and locally rare and common plant species from Switzerland. We accounted for differences in a plant's growth and competitive strategy and habitat resource availability. We found that regionally and locally rare and common plant species did not generally differ in their resistance to most generalist herbivores. However, one herbivore species even performed better and preferred locally and regionally common plant species over rarer ones, indicating that common species are not more resistant, but tend to be less resistant. We also found that all herbivore species consistently performed better on competitive and large plant species, although different herbivore species generally preferred and performed better on different plant species. The latter indicates that the use of generalist herbivores as indicators of plant-resistance levels can be misleading. Synthesis: Our results show that rare plant species are not inherently less resistant than common ones to herbivores. Instead, our results suggest that the ability of plants to allocate resources away from defence towards enhancing their competitive ability might have allowed plants to tolerate herbivory, and to become locally and regionally common."},{"pid":"wsl:32658","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:32658","citation":{"WSL":"Caye Daudt R., Wulf H., Hafner E.D., Bühler Y., Schindler K., Wegner J.D. (2023) Snow depth estimation at country-scale with high spatial and temporal resolution ISPRS J. Photogramm. Remote Sens. 197, 105-121. https://doi.org/10.1016/j.isprsjprs.2023.01.017"},"doi":"10.1016/j.isprsjprs.2023.01.017","abstract":"Monitoring snow depth is important for applications such as hydrology, energy planning, ecology, and safety evaluation for outdoor winter activities. Most methods able to estimate snow depth for large regions can only do so in a spatial resolution of up to 1 km ground sampling distance (GSD). This limits their usage in high alpine areas, where this resolution fails to capture local snow distribution patterns caused by the pronounced topographical features. In this work we use a recurrent convolutional neural network to estimate snow depth at high spatial resolution (10 m GSD), weekly, and at large scale based on satellite data sources and elevation maps, without the need for measurement stations on the ground. The proposed method achieves unprecedented results for large-scale, high-resolution snow depth mapping. The resulting maps are evaluated over a period of three years against high-fidelity snow depth maps obtained with airborne photogrammetry. Finally, we also produce well-calibrated uncertainty estimates for every individual snow depth estimate via a probabilistic regression framework."},{"pid":"wsl:33413","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:33413","citation":{"WSL":"Cremona A., Huss M., Landmann J.M., Borner J., Farinotti D. (2023) European heat waves 2022: contribution to extreme glacier melt in Switzerland inferred from automated ablation readings Cryosphere 17(5), 1895-1912. https://doi.org/10.5194/tc-17-1895-2023"},"doi":"10.5194/tc-17-1895-2023","abstract":"Accelerating glacier melt rates were observed during the last decades. Substantial ice loss occurs particularly during heat waves that are expected to intensify in the future. Because measuring and modelling glacier mass balance on a daily scale remains challenging, short-term mass balance variations, including extreme melt events, are poorly captured. Here, we present a novel approach based on computer-vision techniques for automatically determining daily mass balance variations at the local scale. The approach is based on the automated recognition of colour-taped ablation stakes from camera images and is tested and validated at six stations installed on three Alpine glaciers during the summers of 2019-2022. Our approach produces daily mass balance with an uncertainty of ±0.81 cm w.e. d-1, which is about half of the accuracy obtained from visual readouts. The automatically retrieved daily mass balances at the six sites were compared to average daily mass balances over the last decade derived from seasonal in situ observations to detect and assess extreme melt events. This allows analysing the impact that the summer heat waves which occurred in 2022 had on glacier melt. Our results indicate 23 d with extreme melt, showing a strong correspondence between the heat wave periods and extreme melt events. The combination of below-average winter snowfall and a suite of summer heat waves led to unprecedented glacier mass loss. The Switzerland-wide glacier storage change during the 25 d of heat waves in 2022 is estimated as 1.27 ± 0.10 km3 of water, corresponding to 35 % of the overall glacier mass loss during that summer. The same 25 d of heat waves caused a glacier mass loss that corresponds to 56 % of the average mass loss experienced over the entire melt season during the summers 2010-2020, demonstrating the relevance of heat waves for seasonal melt."}]

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