Dr. Michael Bründl

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.

Climate change is a global challenge with serious impacts on human populations. Numerous studies have highlighted the impacts of climate change on natural hazard processes and associated risks for communities. Understanding future hazard and risks is crucial for effective risk management. This study focuses on assessing snow avalanche risks for inhabited areas in the context of climate-induced changes. By using hazard scenarios based on CH2018 climate projections and the RAMMS avalanche model, we generated large-scale hazard indication maps for future avalanche hazards. By employing the open-source probabilistic risk assessment platform CLIMADA, along with building data and vulnerability functions, we estimated risks for the present time and two future time frames: mid-century (2060) and the end of the century (2085). An uncertainty and sensitivity analysis complemented the study to account for potential fluctuations in model assumptions. Our mean-based approach, considering different CH2018 model chains, indicates an overall decline in avalanche risks for the future. The average annual impact for the medium (100-year return period) scenario decreases from 2.73 million CHF/Year to 1.75 million CHF/Year in mid-century, to 0.69 million CHF/Year by end of the century. This reduction is driven by assumed decreases in snow accumulation, rising snowpack temperatures, and a rising snowline. To cover more extreme developments, we have also examined boundary model chains, which suggest that future risks can both increase and decrease depending on minimum or maximum extreme precipitation. Within our model assumptions, both showed a general trend of decreasing affected objects towards the end of the century. In the extreme minimum snowfall scenario risk decreases from 1.85 of today to 0.3 million CHF/Year in mid-century and to 0.18 million CHF/Year by the end of the century. On the other hand, in the extreme maximum snowfall scenario risk increases to 4.29 million CHF/Year in mid-century but also decreases to 2.01 million CHF/Year by the end of the century. In the maximum snowfall scenarios, the reduction is mostly driven by a rising snowfall threshold and rising snow cover temperatures. It is worth noting that some individual objects depending on their location may remain at consistently high avalanche risk despite climate change. This study provides a valuable tool for decision-makers to compare future risk scenarios with the present situation, supporting effective mitigation and adaptation strategies to address the challenges of climate change. By providing risk maps and identifying potential future risk hot spots, our approach contributes to enhancing community resilience and protecting their assets in a changing climate.

It is best practice to evaluate the cost-efficiency of different road cut slope stabilization measures, prior to designing new cut slopes or stabilizing existing ones. This can be done by conducting a cost analysis. Most cost analysis methodologies require large datasets that are costly and time-consuming to establish (e.g. databases of historical data or in-situ test results). We present a new cost–benefit analysis (CBA) methodology based on direct cost estimates and a rigorous but parsimonious mechanistic and probabilistic geotechnical slope stability assessment that can be used to evaluate the cost-efficiency of different stabilization measures for a single-cut slope. Probabilistic stability analyses are coupled with a hillslope-hydrological model (the hillslope-storage Boussinesq model) based on the CUTSTAB-P method to determine the frequency of a cut slope failure over a prescribed period. By determining the frequency of the cut slope failure, the cost of failure (remediation) over a prescribed period is established. The cost of failure for a particular cut slope design is combined with the initial upfront investment and running maintenance costs to determine the cost efficiency of implementing the stabilization measures over the entire cut slope lifetime. This methodology is suitable to compare the cost efficiency of many different stabilization designs. Unlike other cost analyses for slope stability, our methodology accounts for uncertainty in slope geomaterial characteristics, as well as for hillslope hydrology.

According to various projections, climate change will alter the disposition for alpine mass movements, as well as their dynamics and the interaction of gravitational processes in process cascades. This will change the risks that people living in mountain regions are exposed to. The research program CCAMM - Climate Change Impacts on Alpine Mass Movements – initiated by the Swiss Federal Institute for Forest, Snow and Landscape Research WSL, fosters inter- and transdisciplinary research and thus addresses a socially relevant question and provides an important contribution to climate change adaptation of society. In this contribution, we provide an overview of the 22 projects and the envisioned outreach activities in 2025.

Mortality rates are used as a basis for defining a reference value for the risk of being killed from gravitational natural hazards in Switzerland. We present an updated analysis of these mortality rates as the population and its structure are changing over time. The lowest mortality rates have been decreasing over the past decades. The reference value for the risk of dying from gravitational natural hazards is now less than an order of magnitude below the lowest mortality rates.
The average yearly number of fatalities from gravitational natural hazards over the past two decades has been 4. The number of heat-related fatalities has been a factor of 89 higher but compared to the averaged overall number of fatalities in the age classes, it is still more than an order of magnitude smaller. We put heat-related fatalities into perspective with fatalities from gravitational natural hazards because heatwaves are expected to become more intense and more frequent with climate change.

Specific impacts of climate change on snow avalanche risk for inhabited areas are largely unknown and call for further investigation. Numerous studies suggest that expected increasing temperatures and changes in precipitation could have significant effects on the release and flow characteristics of snow avalanches. To assess the possible consequences of potential changes in snow accumulation and temperature and their subsequent impact on avalanche hazard and risk, we introduce a comprehensive framework for modelling avalanche risk at large scale, incorporating climate change scenarios. By applying a down-scaling procedure, we processed data from the CH2018 Swiss climate change scenarios within the extreme RCP8.5 emission scenario considering six different climate model chains. This data set is used to simulate potential snowcovers of 100 future winters for each of the selected model chain with the physical snowcover model SNOWPACK. Return period scenarios with future avalanche fracture depths are defined for the mid (2060) and end of the century (2085) by applying methods of extreme value statistics. Within these periods, potential future snowcover temperatures are analyzed and compared. The changed parameters serve as input for the research version of the established avalanche simulation software RAMMS. Generated large scale hazard indication maps are combined with the probabilistic risk assessment platform CLIMADA. The output are spatially explicit hazard and risk maps that illustrate possible climate change effects on avalanche risk and allow the quantification of potential future changes. Avalanche risk maps can illustrate the potential effects of climate change on snow avalanches, thus serving as a foundation for assessing future risk assessment and effective strategies to address climate change-related objectives.

We introduce a comprehensive framework for modelling avalanche hazard and risk to buildings at large scale considering climate change scenarios. Based on downscaled data from the CH2018 Swiss climate change scenarios, we simulate the thickness and structure of future snow cover of 100 future winters for six model chains using the physical model SNOWPACK and derive potential future fracture depths as well as future snow temperature for three return period scenarios for the mid (2060) and the end of the century (2085). This data serves as input for the research version of the avalanche simulation software RAMMS::EXTENDED. The resulting hazard indication maps are used for a risk assessment using the platform CLIMADA. The resulting hazard indication and risk maps illustrate potential effects of climate change on the spatial distribution of avalanche induced risks to buildings and highlight that, depending on the scenarios, a trend towards reduced building risks can be observed.

Cost-benefit analyses are conducted to evaluate the cost efficiency of road slope stabilisation measures to aid road planning, design, maintenance, and repair. Most cost analyses are based on a statistical framework that requires a database of slope failures. However, databases can be costly to compile, and they tend to compare options that satisfy the same global factor of safety or partial factors of safety (e.g. EC-7) neglecting the fact that each measure reduces the risk of slope failure by a different extent. Here, we present a novel methodology to evaluate the cost efficiency of different road slope stabilisation measures based on direct costs and a rigorous but parsimonious mechanistic and probabilistic geotechnical slope stability assessment. Unlike other cost analyses for slope stability, our methodology accounts for uncertainty in slope geomaterial characteristics, as well as for hillslope hydrology. Probabilistic slope stability analyses accounting for the effect of time-varying slope seepage are performed using the CUTSTAB-P methodology to estimate the frequency of slope failure. The methodology is demonstrated on a cut slope in Nepal, assessing four different road slope stabilisation measures that are implemented in Nepal: (1) the cut slope with no additional support; (2) reprofiling to a shallower inclination; (3) a mortared masonry wall; and (4) an anchoring system. We find that an anchoring system is the most cost-efficient road slope stabilisation measure for this cut slope, and that a mortared masonry wall is least cost-efficient. This is despite the mortared masonry wall having much lower initial investment costs than the anchoring system. Mortared masonry walls are hugely common along roads in Nepal. We also make an approximation of indirect costs. With this addition, we find that the anchoring system remains the most cost-efficient method.

Der Begriff «Risiko» ist in der Schweiz seit Anfang 2000 und insbesondere seit dem ersten Erscheinen der PLANAT-Strategie im Jahr 2003 und seiner überarbeiteten Version im Jahr 2018 in immer grösser werdenden Mass in den Fokus beim Umgang mit Naturgefahren gerückt. Seitdem werden nicht nur die Gefährdungen, sondern auch ihre Auswirkungen auf die Menschen, die von ihnen erbauten Gebäude und Infrastrukturen sowie Kulturgüter als handlungsleitend bei der Ergreifung von Schutz- und Anpassungsmassnahmen betrachtet. Mit den immer deutlicher werdenden Auswirkungen des Klimawandels rücken neben den Risiken infolge Naturgefahren auch die Risiken für die belebte Umwelt in das Zentrum des Interesses.
In diesem Forum für Wissen beleuchten wir die zahlreichen und schnellen Veränderungen, die wir in Umwelt und Gesellschaft wahrnehmen und die damit verbundenen Risiken. In vier Vorträgen werden ausgehend von den geltenden Klimaszenarien, die Einflüsse auf die Biodiversität, die gravitativen Massenbewegungen und der Umgang der Praxis mit diesen Veränderungen präsentiert und diskutiert.

Snow avalanches are recurring natural hazards that affect the population and infrastructure in mountainous regions, such as in the recent avalanche winters of 2018 and 2019, when considerable damage was caused by avalanches throughout the Alps. Hazard decision makers need detailed information on the spatial distribution of avalanche hazards and risks to prioritize and apply appropriate adaptation strategies and mitigation measures and thus minimize impacts. Here, we present a novel risk assessment approach for assessing the spatial distribution of avalanche risk by combining large-scale hazard mapping with a state-of-the-art risk assessment tool, where risk is understood as the product of hazard, exposure and vulnerability. Hazard disposition is modeled using the large-scale hazard indication mapping method RAMMS::LSHIM (Rapid Mass Movement Simulation::Large-Scale Hazard Indication Mapping), and risks are assessed using the probabilistic Python-based risk assessment platform CLIMADA, developed at ETH Zürich. Avalanche hazard mapping for scenarios with a 30-, 100- and 300-year return period is based on a high-resolution terrain model, 3 d snow depth increase, automatically determined potential release areas and protection forest data. Avalanche hazard for 40 000 individual snow avalanches is expressed as avalanche intensity, measured as pressure. Exposure is represented by a detailed building layer indicating the spatial distribution of monetary assets. The vulnerability of buildings is defined by damage functions based on the software EconoMe, which is in operational use in Switzerland. The outputs of the hazard, exposure and vulnerability analyses are combined to quantify the risk in spatially explicit risk maps. The risk considers the probability and intensity of snow avalanche occurrence, as well as the concentration of vulnerable, exposed buildings. Uncertainty and sensitivity analyses were performed to capture inherent variability in the input parameters. This new risk assessment approach allows us to quantify avalanche risk over large areas and results in maps displaying the spatial distribution of risk at specific locations. Large-scale risk maps can assist decision makers in identifying areas where avalanche hazard mitigation and/or adaption is needed.

In der Schweiz erlaubt das Werkzeug EconoMe seit 2008 eine risikobasierte Vorgehensweise im Schutz gegen Naturgefahren. Sowohl die Plattform als auch die Methodik von EconoMe wurden und werden stetig weiterentwickelt. Dieser Artikel gibt einen Überblick über die neuesten und wesentlichsten Änderungen und zeigt die Bedeutung von EconoMe aus Kantons- und Bundessicht. Mit einem Ausblick zu bevorstehenden Arbeiten und den zu überwindenden Hürden schließt der Artikel ab.

Since 2008, the tool EconoMe has enabled Switzerland to adopt a risk-based approach to dealing with natural hazards. The EconoMe online platform as well as the methodology have continuously been developed, a process which is still ongoing. This article gives an overview of the newest and most meaningful changes and shows the importance of EconoMe as seen from a cantonal and a federal perspective. An outlook on upcoming tasks and some expected challenges brings the article to an end.

In January 2018, heavy snowfalls caused an extraordinary avalanche situation in Switzerland with an extent not observed since the avalanche winter of 1999. The amount of precipitation was far above the long-term average und in parts of the Swiss Alps even twice the average. For the first time since 1999, the highest danger level 5-Very High was forecast for a 36-hour period and for most regions of the Swiss Alps. We present key findings of the analysis of this extraordinary event and show that the mitigation efforts taken after the catastrophic events in February 1999 were effective. Despite very high avalanche activity, there was no loss of life and damage to property was limited.

Snow avalanches can pose a risk to persons, buildings, and infrastructure in mountain regions. As long as people have settled in the Alps, they had to deal with avalanche hazard. Structural mitigation measures, protection forests, and land-use planning reduced the hazard and the risk in past decades and contributed thereby to the development of mountain regions. In many countries, decisions on dealing with the consequences of avalanches are increasingly based on the assessment of risks and not only on the reduction of hazard. In the first part of this chapter, we present different elements of an integrative risk management of avalanches with a focus on Switzerland. In the second part, we present an example of how this concept can be applied to handle the avalanche risk in the City of Juneau, Alaska.

Gemäss verschiedenen Abschätzungen wird sich durch die Klimaveränderung nicht nur die Disposition für alpine Massenbewegungen, sondern auch deren Dynamik und die Interaktion von gravitativen Prozessen bzw. deren Verkettung in Prozesskaskaden verändern. Dies wird zu einem veränderten Risiko für die Schweizer Bevölkerung in Bezug auf alpine Massenbewegungen führen.
Das WSL Forschungsprogramm CCAMM - Climate Change Impacts on Alpine Mass Movements untersucht die Auswirkungen des Klimawandels auf alpine Massenbewegungen, um die daraus resultierenden Risiken besser abzuschätzen und geeignete Anpassungsstrategien für die Gesellschaft zu entwickeln. Im Folgenden stellen wir das WSL-Forschungsprogramm CCAMM vor.

Selon diverses estimations, le changement climatique modifiera non seulement la disposition des mouvements de masse alpins, mais aussi leur dynamique et l'interaction des processus gravitationnels ou leur enchaînement en cascade. Cela entraînera un changement de risque pour la population suisse par rapport aux mouvements de masse alpins.
Le programme de recherche du WSL CCAMM - Climate Change Impacts on Alpine Mass Movements - étudie les effets du changement climatique sur les mouvements de masse alpins afin de mieux évaluer les risques résultants et de développer des stratégies d'adaptation appropriées pour la société. Nous présentons ci-après le programme de recherche du WSL CCAMM.

Affluence and vulnerability are often seen as opposite sides of a coin - with affluence generally understood as reducing forms of vulnerability through increased resilience and adaptive capacity. However, in the context of climate change and an increase in associated hazards and disasters, we suggest the need to re-examine this dynamic relationship - a complex association we define here as the Affluence-Vulnerability Interface (AVI). We review research in different national contexts to show how a more nuanced understanding of the AVI can (a) problematize the notion that increasing material affluence necessarily has a mitigating influence on social vulnerability, (b) extend our analysis of social vulnerability beyond low-income regions to include affluent contexts and (c) improve our understanding of how psychosocial characteristics influence people's vulnerability. Finally, we briefly outline three methodological approaches that we believe will assist future engagement with the AVI.

Over the past 30 years, dealing with natural hazards in Switzerland has changed from being hazard-oriented to using a risk-oriented approach. After a series of catastrophic events, the National Strategy Natural Hazards was published in 2004 and updated in 2018. Following this strategy, various methods and tools were developed. We present some of these developments and give an example of risk-oriented planning for structural avalanche protection measures using the tool EconoMe. The results of the quantitative risk assessment and the benefit-cost-analysis indicate that the planned measures can be recommended for subsidisation.