Avalanche Danger Research Articles

The Missing Link between Terrain-Induced Potential Vorticity Banners and Banded Convection

AbstractOn 1 February 2014, the southern side of the Alps was affected by a severe snowstorm that forced authorities to issue the highest level of avalanche danger in southern parts of Austria. The northern side of the Alps was mostly dry. Nevertheless, radar imagery captured the evolution of quasi-steady convective cloud bands over the northern Alpine foreland with a remarkable length of up to 300 km. This study illuminates the processes that generated these cloud bands based on numerical simulations. The storm was associated with a deep large-scale trough that caused strong southwesterly cross-Alpine flow, orographic precipitation on the southern side, and foehnlike subsidence on the northern side of the Alps. Orographic potential vorticity (PV) banners developed at small-scale topographic features embedded in the Alps and extended downstream over the northern Alpine foreland. Convective cloud bands were aligned parallel to these PV banners. They formed in an environment of inertial instability (negative absolute vorticity) and conditional instability. Sensitivity experiments reveal that the structure and size of these cloud bands are strongly sensitive to the small-scale terrain roughness. Removing small-scale topographic features suppresses the formation of orographic vorticity banners, which in turn suppresses the development of cloud bands. These results suggest that the release of inertial instability at negative orographic vorticity banners was crucial for establishing circulations and associated uplift that triggered conditional instability. To summarize, inertial instability was most likely responsible for the banded structure and conditional instability for the convective nature of these cloud bands.

Ski touring in Poland: Who takes part in this form of specialised tourism? How do they take part and why?

The article presents a description of ski touring by Polish tourists. The author is looking for answers to the following questions: Who goes on this form of tourism? How and why? How experienced are the tourists? Are they aware of the risks involved? Are they theoretically and practically prepared for the danger of avalanches? The author compares their social features and tourist-recreational behaviour to research conducted by the Central Statistical Office in 2012.

Which are the highest peaks in the US Arctic? Fodar settles the debate

Abstract. Though an outstanding achievement for their time, the United States Geological Survey (USGS) topographic maps of the eastern Alaskan Arctic nonetheless contain significant errors, and in this paper we address one of them. Specifically, USGS maps of different scale made in the late 1950s alternate between Mt. Chamberlin and Mt. Isto as the tallest peak in the US Arctic. Given that many of the peaks here are close in height and covered with glaciers, recent climate change may also have changed their height and their order. We resolved these questions using fodar, a new airborne photogrammetric technique that utilizes structure-from-motion (SfM) software and requires no ground control, and validated it using GPS measurements on the peaks as well as airborne lidar. Here we show that Mt. Chamberlin is currently the third tallest peak and that the order and elevations of the five tallest mountains in the US Arctic are Mt. Isto (2735.6 m), Mt. Hubley (2717.6 m), Mt. Chamberlin (2712.3 m), Mt. Michelson (2698.1 m), and an unnamed peak (2694.9 m); these heights are relative to the NAVD88 GEOID12A vertical datum. We find that it is indeed plausible that this ranking has changed over time and may continue to change as summit glaciers continue to shrink, though Mt. Isto will remain the highest under current climate trends. Mt. Isto is also over 100 m taller than the highest peak in Arctic Canada, making it the highest peak in the North American Arctic. Fodar elevations compared to within a few centimeters of our ground-based GPS measurements of the peaks made a few days later and our complete validation assessment indicates a measurement uncertainty of better than ±20 cm (95 % RMSE). By analyzing time series of fodar maps, we were able to detect topographic change on the centimeter level on these steep slopes, indicating that fodar can be used to measure mountain snow packs for water resource availability or avalanche danger, glacier volume change, and slope subsidence, as well as many other applications of benefit to society. Compared to lidar, the current state-of-the-art airborne topographic mapping, we found this SfM technique as accurate, more useful scientifically, and significantly less expensive, suggesting that fodar is a disruptive innovation that will enjoy widespread usage in the future.

Smartphone applications for communicating avalanche risk information – a study on how they are developed and evaluated by their providers

Abstract. Every year, people are victims of avalanches. It is commonly assumed that one way to decrease those losses is to inform about danger levels. This paper presents a study on current practices in the development and evaluation of smartphones applications that are dedicated to avalanche risk communication. The analysis based on semi-structured interviews with developers of six smartphone apps highlights the context of their development, how choices of content and visualization were made and how their effectiveness is evaluated by the developers themselves. It appears that all these communicators agree on the message to disseminate and the general representation concepts (i.e., use of the international avalanche danger scale and of a tiered approach). However, the specific ways this message is presented (e.g., maps, icons) is not uniform. Moreover, only simple evaluation processes (e.g., usage monitoring) are conducted by the developers. However, they are well aware that further efforts need to be made in order to thoroughly analyze the effectiveness of the smartphone apps in terms of their real impact (e.g., increase in awareness or change in behavior). This work also highlighted that the smartphone applications are in transition from being one-way communication tools to becoming two-way communication platforms, with the possibility for non-experts users to report on snow and avalanche conditions. This paper indicates challenges that avalanche risk communication is facing, although it is indisputably the most advanced and standardized practice compared to communication tools for other natural hazards. In addition to being relevant for the avalanche risk communication community, this research is therefore of interest for scientists and practitioners working on risk communication related to natural hazards.

Treed Avalanche Forecasting: Mitigating Avalanche Danger Utilizing Bayesian Additive Regression Trees

AbstractLittle Cottonwood Canyon Highway is a dead‐end, two‐lane road leading to Utah's Alta and Snowbird ski resorts. It is the only road access to these resorts and is heavily traveled during the ski season. Professional avalanche forecasters monitor this road throughout the ski season in order to make road closure decisions in the face of avalanche danger. Forecasters at the Utah Department of Transportation (UDOT) avalanche guard station at Alta have maintained an extensive daily winter database on explanatory variables relating to avalanche prediction. Whether or not an avalanche crosses the road is modeled in this paper via Bayesian additive tree methods. Utilizing daily winter data from 1995 to 2011, results show that using Bayesian tree analysis outperforms traditional statistical methods in terms of realized misclassification costs that take into consideration asymmetric losses arising from two types of error. Closing the road when an avalanche does not occur is an error harmful to resort owners, and not closing the road when one does may result in injury or death. Copyright © 2016 John Wiley & Sons, Ltd.

The hidden risk in user-generated content: An investigation of ski tourers' revealed risk-taking behavior on an online outdoor sports platform

This paper investigates risk-taking behavior in the context of an online outdoor sports platform. Analyzing a unique behavioral dataset of 6242 ski tours completed over a time period of eight winter seasons, this paper shows that the accuracy of user-generated content on ski tours is limited and that more than one third of ski tours accessible on the respective online platform was relatively dangerous on the particular days according to a common avalanche risk assessment method. The quantitative analysis furthermore reveals that at avalanche danger level “considerable” more than sixty percent of ski tours were relatively dangerous. Overall, this paper provides novel insights into risks that come with user-generated content in the adventure tourism and adventure recreation domain and derives important implications for online platform users, online platform providers, public institutions, and tourism destinations.

Variability of the snow avalanche danger in the Tatra Mountains during the past nine decades

In order to recognise the variability of the snow avalanche danger in the Tatra Mountains, the danger levels on consecutive days with snow cover over the last nine decades were calculated. To accomplish this task, the longest series of meteorological data were used from the Tatras along with an empirical method for determining the regional avalanche danger on the basis of elementary meteorological data. The results point to the fact that over the last 25 years the number of days with a level 2 avalanche danger significantly decreased, whereas the number of days with level 1 increased. This should result in a decreasing trend in the incidence of small and medium-sized natural avalanches. In the structure of snow cover, the percentage of melt forms might increase. However, this should not correlate with a significant increase in wet-snow avalanches, because the number of days with wet snow also reduces. The contemporary changes in the snow conditions and avalanche danger in the subalpine belt of the Tatras have been primarily associated with an increase in the air temperature (shorter winters and less snow).

EXPERIENCE WITH THE ANTI-AVALANCHE STRUCTURES IN THE ELBRUS REGION

Приэльбрусье характеризуется очень высокой степенью лавинной опасности. В верховьях долины р. Баксан построены автомобильная дорога, канатные дороги, гостиницы, кафе и другие сооружения. В многоснеж- ные зимы все они находятся в зоне лавинной опасности, поэтому в 2008 г. в верховьях Баксанской долины, над поляной Азау, впервые на лавиноопасном склоне были установлены снегоудерживающие щиты. Рас- смотрены первый опыт строительства и функционирования зтих противолавинных сооружений, а также эффективность их работы в зимы 2008/09 и 2009/10 гг. Даны рекомендации по реконструкции имеющихся и вновь возводимых сооружений на лавиноопасных склонах.

Analysis of avalanche risk factors in backcountry terrain based on usage frequency and accident data in Switzerland

Abstract. Recreational activities in snow-covered mountainous terrain in the backcountry account for the vast majority of avalanche accidents. Studies analyzing avalanche risk mostly rely on accident statistics without considering exposure (or the elements at risk), i.e., how many, when and where people are recreating, as data on recreational activity in the winter mountains are scarce. To fill this gap, we explored volunteered geographic information on two social media mountaineering websites – bergportal.ch and camptocamp.org. Based on these data, we present a spatiotemporal pattern of winter backcountry touring activity in the Swiss Alps and compare this with accident statistics. Geographically, activity was concentrated in Alpine regions relatively close to the main Swiss population centers in the west and north. In contrast, accidents occurred equally often in the less-frequented inner-alpine regions. Weekends, weather and avalanche conditions influenced the number of recreationists, while the odds to be involved in a severe avalanche accident did not depend on weekends or weather conditions. However, the likelihood of being involved in an accident increased with increasing avalanche danger level, but also with a more unfavorable snowpack containing persistent weak layers (also referred to as an old snow problem). In fact, the most critical situation for backcountry recreationists and professionals occurred on days and in regions when both the avalanche danger was critical and when the snowpack contained persistent weak layers. The frequently occurring geographical pattern of a more unfavorable snowpack structure also explains the relatively high proportion of accidents in the less-frequented inner-alpine regions. These results have practical implications: avalanche forecasters should clearly communicate the avalanche danger and the avalanche problem to the backcountry user, particularly if persistent weak layers are of concern. Professionals and recreationists, on the other hand, require the expertise to adjust the planning of a tour and their backcountry travel behavior depending on the avalanche danger and the avalanche problem.

Avalanche hazard in plain area of Sakhalin Island

Рассмотрены факторы формирования лавин на равнинных территориях о. Сахалин, где на низменных участках встречаются положительные формы рельефа с превышением 5–30 м и средним уклоном более 25° (дюны, бугры пучения, просадочные впадины, речные террасы и речные обрывы). Установлены случаи схода лавин со склонов с превышением до 50 м, в результате которых гибли люди. Именно поэтому необходима оценка степени лавинной опасности не только горных территорий, но и участков с низкой площадной поражённостью лавинными процессами.

A Hidden Markov Model for avalanche forecasting on Chowkibal–Tangdhar road axis in Indian Himalayas

A numerical avalanche prediction scheme using Hidden Markov Model (HMM) has been developed for Chowkibal–Tangdhar road axis in J&K, India. The model forecast is in the form of different levels of avalanche danger (no, low, medium, and high) with a lead time of two days. Snow and meteorological data (maximum temperature, minimum temperature, fresh snow, fresh snow duration, standing snow) of past 12 winters (1992–2008) have been used to derive the model input variables (average temperature, fresh snow in 24 hrs, snow fall intensity, standing snow, Snow Temperature Index (STI) of the top layer, and STI of buried layer). As in HMMs, there are two sequences: a state sequence and a state dependent observation sequence; in the present model, different levels of avalanche danger are considered as different states of the model and Avalanche Activity Index (AAI) of a day, derived from the model input variables, as an observation. Validation of the model with independent data of two winters (2008–2009, 2009–2010) gives 80% accuracy for both day-1 and day-2. Comparison of various forecasting quality measures and Heidke Skill Score of the HMM and the NN model indicate better forecasting skill of the HMM.

A qualitative analysis of group formation, leadership and decision making in recreation groups traveling in avalanche terrain

The popularity of recreational activities in avalanche terrain has increased dramatically in recent years. Venturing into such terrain also increases the personal risk of injury or death. Whereas the majority of recreationists travel in groups, existing research on the human dimension of avalanche safety has primarily focused on individual decision making. This empirical study aims to fill this gap by investigating aspects of group formation, leadership and decision making among winter recreationists with respect to their ability to make safe decisions when traveling in avalanche terrain. We used a qualitative research design and conducted 29 semi-structured group interviews with backcountry skiers and off-piste skiers in Switzerland during the winter of 2013. Our results show that while the majority of the reported behaviors and strategies are effective at reducing avalanche risk (e.g., traveling in well-established groups or deciding on the basis of well-known avalanche safety rules), others are highly problematic (e.g., traveling in emergent groups or trivializing decisions concerning avalanche danger). The identified behavioral patterns offer valuable insight for the development of effective avalanche safety messages to address weaknesses in group dynamics. Management implicationsSince most recreationists travel in groups when visiting avalanche terrain, group dynamics are a crucial component of avalanche safety, and a better understanding of group behaviors is imperative for safe traveling. We urge avalanche safety educators to put more emphasis on the role of group formation, leadership and decision making for avalanche safety. While strategies known to improve group performance should be encouraged, educators should also highlight the risks associated with the more problematic behaviors explicitly. We propose the development of a group checklist to facilitate the group formation process.

Upward-looking L-band FMCW radar for snow cover monitoring

Forecasting snow avalanche danger in mountainous regions is of major importance for the protection of infrastructure in avalanche run-out zones. Inexpensive measurement devices capable of measuring snow height and layer properties in avalanche starting zones may help to improve the quality of risk assessment. We present a low-cost L-band frequency modulated continuous wave radar system (FMCW) in upward-looking configuration. To monitor the snowpack evolution, the radar system was deployed in fall and subsequently was covered by snowfalls. During two winter seasons we recorded reflections from the overlying snowpack. The influence of reflection magnitude and phase to the measured frequency spectra, as well as the influence of signal processing were investigated. We present a method to extract the phase of the reflection coefficients from the phase response of the frequency spectra and their integration into the presentation of the measurement data. The phase information significantly improved the detectability of the temporal evolution of the snow surface reflection. We developed an automated and a semi-automated snow surface tracking algorithm. Results were compared with independently measured snow height from a laser snow-depth sensor and results derived from an upward-looking impulse radar system (upGPR). The semi-automated tracking used the phase information and had an accuracy of about 6 to 8cm for dry-snow conditions, similar to the accuracy of the upGPR, compared to measurements from the laser snow-depth sensor. The percolation of water was observable in the radargrams. Results suggest that the upward-looking FMCW system may be a valuable alternative to conventional snow-depth sensors for locations, where fixed installations above ground are not feasible.

GIS-aided avalanche warning in Norway

Avalanche warning for large areas requires the processing of an extensive amount of data. Information relating to the three basic requirements for avalanche warning – knowledge of terrain, the snow conditions, and the weather – needs to be available for the forecaster. The information is highly variable in time. The form and visualization of the data is often decisive for the use by the avalanche forecasters and therefore also for the quality of the produced forecasts. Avalanche warnings can be issued at different scales from national to regional and down to object specific. Often the same warning service is working at different scales and for different clients requiring a flexible and scalable approach. The workflow for producing avalanche forecasts must be extremely efficient – all the way from acquiring observation data, evaluating the situation, down to publishing the new forecast. In this study it has been an aim to include the entire workflow in a single web application. A Geographic Information Systems (GIS) solution was chosen to include all data needed by the forecaster for the avalanche danger evaluation. This interactive system of maps features background information for the entire country, such as topographic maps, slope steepness, aspect, hill shades and satellite images. In each avalanche warning area, all active avalanche paths are plotted including information on wind exposure. Each avalanche path is linked to a webpage with more details, such as fall height, release area elevation and pictures. The avalanche path webpage also includes information on the object at risk e.g. buildings, roads, or other objects. Thus, the forecaster can easily get an overview on the overall situation and focus on single avalanche paths to generate detailed avalanche warnings for the client.

Adherence of backcountry winter recreationists to avalanche prevention and safety practices in northern Italy

Backcountry recreationists account for a high percentage of avalanche fatalities, but the total number of recreationists and relative percentage of different recreation types are unknown. The aim of this study was to collect the first comprehensive survey of backcountry skiers and snowshoers in a region in the European Alps to quantify adherence to basic prevention and safety practices. Over a 1-week period in February 2011 in South Tyrol, Italy, 5576 individuals (77.7% skiers, 22.3% snowshoers) in 1927 groups were surveyed. Significantly more skiers than snowshoers could report the avalanche danger level (52.5% vs 28.0% of groups) and carried standard rescue equipment (transceiver, probe, and shovel) (80.6% vs 13.7% of individuals). Complete adherence to minimum advisable practices (i.e., an individual being in a group with one member correctly informed about the danger level and carrying personal standard rescue equipment) was 41.5%, but was significantly higher in skiers (51.1% vs 8.7% snowshoers) and in individuals who were younger, reported more tours per season, traveled in larger groups, and started earlier. A transnational survey over a complete winter season would be required to obtain total participation prevalence, detect regional differences, and assess the influence of prevention and safety practices on relative reduction in mortality.

Analysis of the snow-atmosphere energy balance during wet-snow instabilities and implications for avalanche prediction

Abstract. Wet-snow avalanches are notoriously difficult to predict; their formation mechanism is poorly understood since in situ measurements representing the thermal and mechanical evolution are difficult to perform. Instead, air temperature is commonly used as a predictor variable for days with high wet-snow avalanche danger – often with limited success. As melt water is a major driver of wet-snow instability and snow melt depends on the energy input into the snow cover, we computed the energy balance for predicting periods with high wet-snow avalanche activity. The energy balance was partly measured and partly modelled for virtual slopes at different elevations for the aspects south and north using the 1-D snow cover model SNOWPACK. We used measured meteorological variables and computed energy balance and its components to compare wet-snow avalanche days to non-avalanche days for four consecutive winter seasons in the surroundings of Davos, Switzerland. Air temperature, the net shortwave radiation and the energy input integrated over 3 or 5 days showed best results in discriminating event from non-event days. Multivariate statistics, however, revealed that for better predicting avalanche days, information on the cold content of the snowpack is necessary. Wet-snow avalanche activity was closely related to periods when large parts of the snowpack reached an isothermal state (0 °C) and energy input exceeded a maximum value of 200 kJ m−2 in one day, or the 3-day sum of positive energy input was larger than 1.2 MJ m−2. Prediction accuracy with measured meteorological variables was as good as with computed energy balance parameters, but simulated energy balance variables accounted better for different aspects, slopes and elevations than meteorological data.

CO2 partial pressure and calcite saturation in springs – useful data for identifying infiltration areas in mountainous environments

Mountainous regions such as the Central European Alps host considerable karstified or fractured groundwater bodies, which meet many of the demands concerning drinking water supply, hydropower or agriculture. Alpine hydrogeologists are required to describe the dynamics in fractured aquifers in order to assess potential impacts of human activities on water budget and quality. Delineation of catchment areas by means of stable isotopes and hydrochemical data is a well established method in alpine hydrogeology. To achieve reliable results, time series of (at least) one year and spatial and temporal close-meshed data are necessary. In reality, test sites in mountainous regions are often inaccessible due to the danger of avalanches in winter. The aim of our work was to assess a method based on the processes within the carbonic acid system to delineate infiltration areas by means of single datasets consisting of the main hydrochemical parameters of each spring. In three geologically different mountainous environments we managed to classify the investigated springs into four groups. (1) High PCO2 combined with slight super-saturation in calcite, indicating relatively low infiltration areas. (2) Low PCO2 near atmospheric conditions in combination with calcite saturation, which is indicative of relatively high infiltration areas and a fractured aquifer which is not covered by topsoil layers. (3) High PCO2 in combination with sub-saturation in calcite, representing a shallow aquifer with a significant influence of the topsoil layer. (4) The fourth group of waters is characterized by low PCO2 and sub-saturation in calcite, which is interpreted as evidence for a shallow aquifer without significant influence of any hard rock aquifer or topsoil layer. This study shows that CO2-partial pressure can be an ideal natural tracer to estimate the elevation of infiltration areas, especially in non-karstified fractured groundwater bodies.

Learning from the past: statistical performance measures for avalanche warning services

Avalanche warning services (AWS) are operated to protect communities and traffic lines in avalanche-prone regions of the Alps and other mountain ranges. In times of high avalanche danger, these services may decide to close roads or to evacuate settlements. Closing decisions are based on field observations, avalanche release statistics, and snow forecasts issued by weather services. Because of the spatial variability in the snowpack and the insufficient understanding of avalanche triggering mechanisms, closing decisions are characterized by large uncertainties and the information based on which AWS have to decide is always incomplete. In this paper, we illustrate how signal detection theory can be applied to make better use of the information at hand. The proposed framework allows the evaluation of past road closures and points to how the decision performance of AWS could be improved. To illustrate the proposed framework, we evaluate the decision performance of two AWS in Switzerland and discuss the advantages of such a formalized decision-making approach.

A new method for visualizing snow stability profiles

Abstract Snow stability assessment by interpreting snow profiles is a time consuming and fairly subjective process, especially when snow stratigraphy was recorded without performing a stability test at the same time. Snow stratigraphy is clearly related to snow stability, as had been shown by various studies that linked specific snowpack properties such as grain size and type to instability. We suggest a new method to visualize snow stratigraphy in regard to stability based on six structural variables (also known as the threshold sum approach). Each snow layer is represented by the number of variables that are not in the corresponding critical range. This approach has not only been implemented for manually recorded snow profiles but also – after adapting the threshold values – for simulated snow stratigraphy provided by the numerical snow cover model SNOWPACK. The new visualization method, applied both to the manually observed and simulated profiles, was tested by analyzing the most critical avalanche situations of the winter 2008–2009 in the Dolomites (north-eastern Italian Alps). Results indicate that the new visualization method is well suited to quickly and intuitively derive snow stability, in particular from simulated snow stratigraphy. Stability information derived from simulated profiles was clearly related to the independently estimated degree of avalanche danger. Supplementing the snow cover model SNOWPACK with the adjusted threshold sum approach increases its usefulness for avalanche forecasting purposes.

THEORY AND PRACTICE OF INDIVIDUAL SNOW AVALANCHE RISK ASSESSMENT IN THE RUSSIAN ARCTIC

In recent years, the Government of the Russian Federation considerably increased attention to the exploitation of the Russian Arctic territories. Simultaneously, the evaluation of snow avalanches danger was enhanced with the aim to decrease fatalities and reduce economic losses. However, it turned out that solely reporting the degree of avalanche danger is not sufficient. Instead, quantitative information on probabilistic parameters of natural hazards, the characteristics of their effects on the environment and possibly resulting losses is increasingly needed. Such information allows for the estimation of risk, including risk related to snow avalanches. Here, snow avalanche risk is quantified for the Khibiny Mountains, one of the most industrialized parts of the Russian Arctic: Major parts of the territory have an acceptable degree of individual snow avalanche risk ( 1×10 -4 ) degree of individual snow avalanche risk (0.5 and 2% of the total area) correspond to the Southeast of the Khibiny Mountains where settlements and mining industries are situated. Moreover, due to an increase in winter tourism, some traffic infrastructure is located in valleys with an admissible or unacceptable degree of individual snow avalanches risk.