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1.
Snow avalanches are a major natural hazard for road users and infrastructure in northern Gaspésie. Over the past 11 years, the occurrence of nearly 500 snow avalanches on the two major roads servicing the area was reported. No management program is currently operational. In this study, we analyze the weather patterns promoting snow avalanche initiation and use logistic regression (LR) to calculate the probability of avalanche occurrence on a daily basis. We then test the best LR models over the 2012–2013 season in an operational forecasting perspective: Each day, the probability of occurrence (0–100%) determined by the model was classified into five classes avalanche danger scale. Our results show that avalanche occurrence along the coast is best predicted by 2 days of accrued snowfall [in water equivalent (WE)], daily rainfall, and wind speed. In the valley, the most significant predictive variables are 3 days of accrued snowfall (WE), daily rainfall, and the preceding 2 days of thermal amplitude. The large scree slopes located along the coast and exposed to strong winds tend to be more reactive to direct snow accumulation than the inner-valley slopes. Therefore, the probability of avalanche occurrence increases rapidly during a snowfall. The slopes located in the valley are less responsive to snow loading. The LR models developed prove to be an efficient tool to forecast days with high levels of snow avalanche activity. Finally, we discuss how road maintenance managers can use this forecasting tool to improve decision making and risk rendering on a daily basis.  相似文献   

2.
The occurrence of wet-snow avalanches is, in general, poorly understood. For 20 years (winters of 1975–1976 to 1994–1995), the avalanche activity has been observed in the Dischma valley near Davos (Eastern Swiss Alps). The study area comprises a large starting zone of north-easterly aspect (2,300 m a.s.l.) with several avalanche paths. We have analyzed the occurrence data in combination with meteorological and snowpack data collected at an elevation of 2,090 m a.s.l. During the 20-year observation period, almost 800 wet-snow avalanches were observed, about 4.5 times more loose snow avalanches than slab avalanches. Considering both types of avalanches jointly, snow depth, precipitation and air temperature showed the highest correlation with avalanche activity. Most loose snow avalanches occurred when air temperature was high and/or after a precipitation period. Slab avalanches occurrence was primarily related to warm air temperatures and snowpack properties such as the isothermal state and the existence of capillary barriers. Radiation did not show up as a significant variable. The results suggest that in a transitional snow climate wet-snow avalanches are, as dry snow avalanches, often related to precipitation events, and that wet slab instability strongly depends on snowpack properties in relation to warming of the snowpack and melt water production.  相似文献   

3.
Predictive GIS-Based Model of Rockfall Activity in Mountain Cliffs   总被引：6，自引：1，他引：6  
Rockfall susceptibility has been analysed in mountain cliffs of the Cantabrian Range, North Spain. The main aim of this analysis has been to build a predictive model of rockfall activity from a low number of environmental and geological variables. The rockfall activity has been quantified in a GIS. The cartographic information used shows the spatial distribution of all the recent talus screes as well as their associated source areas in the rock-slopes. The area relation At/Ar (recent talus scree polygon/source basins) in the rock slopes has been used as the rockfall activity indicator. This relation has been validated in 50 pilot rock-slopes and compared with the relation number of recent rock fragments/source basin, obtained from field work. The environmental factors causing rockfall depend on the rock slope situation, and these are: altitude and sun radiation on the rock cliff. The geological factors considered are: lithology, relative position of the main discontinuities with respect to the topographic surface and two morphologic parameters: the roughness and slope gradient. A logistic regression analysis has been applied to a population of 442 limestone and quartzite rock cliffs. The dependent variable is the rockfall activity indicator, which allows the definition of two classes of rock cliff units: low and high activity. The independent variables are altitude, sun radiation (equinox radiation, summer solstice radiation, winter solstice radiation), slope roughness, slope gradient,anisotropy and lithology. Results suggest that it is possible tobuild a valid cartographic predictive model for rockfall activity in mountain rock cliffs from a limited number of easily obtainable variables. The method is especially applicable in massive rock slopes or in regions with uniform rock mass characteristics.  相似文献   

4.
The search to improve protective techniques against natural phenomena such as snow avalanches continues to use classic methods to calculate flexible structures. This paper deals with a new method for designing avalanche protection nets; this method is based on a coupled analysis of both the net structure and the snow mantel using a coupled Lagrangian‐discrete approach. This has led to the development of computational software so that avalanche nets can be easily designed. This tool provides for the evolving forces acting on several parts of the net as a function of the snow situation. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

5.
This article is intended to explain the snow avalanche occurrence, as a natural phenomenon directly influenced by the local natural conditions, for the well-delimited area represented by the Piatra Mica massif, belonging to the Piatra Craiului mountain range (southern Carpathians). In this respect, depending on the factors that may trigger or encourage the avalanches, some vulnerable areas with avalanche occurring conditions have been identified, based on the analysis of the relationships among the factors controlling the avalanche vulnerability in the study area. These factors are mainly represented by the slope aspect, which induces from the very beginning some specific features for each type of slope (north-, east-, south and west-facing slopes), the geological structure, slope gradient and topography. At the same time, the general climatic and biological features have been taken into account, from the point of view of their importance for avalanche occurrence and distribution. Depending on the microrelief exhibited by the avalanche chutes, one can establish distinct dynamical features for each of the four major slopes of the massif. It is worth mentioning that for this study area, this is the first paper dealing with avalanche phenomenon, vulnerable space, control factors and landscape dynamics. In accomplishing this demarche, we used detailed mappings in the field in several stages, the processing of satellite images, analytical (declivities, the exposure of slopes, etc.) and synthetic maps from which the dynamic of sectors with avalanches resulted. The findings of this investigation may further be employed for solving the problems raised by avalanche-prone areas, as well as for devising a better strategy for the effective management of the mountain realm.  相似文献   

6.
An avalanche occurrence is a result of the structural collapse of the snow cover in the upper reaches of mountain slopes in the snowbound belt. They take a heavy toll, year after year and property worth millions is destroyed. Besides loss of lives, the avalanches also destroy forest and disrupt road communication, thereby hindering the hill area development and affecting the Defense of the nation.The paper brings out the cause of avalanche formation, magnitude of their destruction power and the techniques being followed in India by Snow and Avalanche Study Establishment (SASE), a DRDO Laboratory, for mitigating the avalanche disasters in Western Himalayan Region for the Defense forces. The authors suggest that for mitigating the avalanche disasters, an integrated plan at national level involving Defense forces and state governments should be drawn.  相似文献   

7.
Snow-supporting avalanche defence structures are increasingly being built at high altitudes in potential permafrost areas. Special construction methods and guidelines have been developed to ensure a minimal stability of the structures, which have a vital role in the protection of underlying settlements and transport infrastructure against snow avalanches. If the avalanche slopes are located on ice-rich permafrost terrain, as is the case in a steep avalanche gully above Pontresina (Eastern Swiss Alps), other means of protection must be used – such as deflection or retention dams – as construction on ice-rich sediments can be very problematic. Experimental snow-supporting structures were built in 1997 in order to test different types of structures and their foundations, to develop specially adapted construction methods and to monitor the long-term behaviour of the structures in moderately creeping frozen ground with volumetric ice contents under 20%. Snow-nets were found to be the most suitable type of protection against avalanches in this type of permafrost terrain due to their deformability and because they are well adapted to rock fall. The structures do not improve slope stability but contribute towards maintaining permafrost as they delay snow melt by modifying the spatial and temporal distribution of the snow cover. The results of the project described have led to a better understanding of permafrost-related avalanche defence problems.  相似文献   

8.
Snow avalanches affect recreation, transportation, resource industries and property. During the 1990s an average of 12.5 persons per year were killed in avalanches in Canada. The snow avalanche hazard has affected people and facilities in B.C, Alberta, Yukon, NWT, Nunavut, Ontario, Quebec and Newfoundland. Avalanche risk may be voluntary, for example skiing and snowmobiling, or involuntary, for example public transportation corridors. A worst-case avalanche scenario is most likely to occur in the Western Cordillera, resulting from a single large-scale weather pattern, where a cold period resulting in the development of a weak layer in the snowpack is followed by a series of major mid-winter storms. Emergency preparedness for avalanches is most advanced in western Canada. New education and information initiatives in Quebec and Newfoundland are aimed at improving preparedness there. Current research is focused on avalanche forecasting, weather forecasting for avalanche prediction, avalanche failure characteristics, forestry and avalanches and geomorphology and avalanches. An important area of future research is the impact of climate change on avalanches, particularly in northern Canada.  相似文献   

9.
Ten monitoring sites were established in 1986 near the Scottbreen and Renardbreen glaciers (Bellsund, Spitsbergen) in order to determine the rates of gelifluction on raised marine terraces and on talus cones, accumulation on talus cones, and movement of the protalus rampart. The measurements were performed in 1987, 2007 and 2016. The results obtained revealed a very slow rate of changes on the surface of the analysed area. During 30 years, only one out of 84 points where the gelifluction rate was measured was displaced by 15 cm down‐slope. The maximal annual and average gelifluction rates were calculated at 0.5 cm and 0.18 cm a?1, respectively. Several measurement points did not change their position over the observation period. As shown by the observations, the gelifluction rate largely does not depend on slope inclination. Studies of talus cones allowed the level of cone increment to be determined as 314.3 kg of scree per square metre. Analysis of factors influencing the rate of mass movement allowed for correlation of the small‐scale gelifluction movement at the analysed sites with the general trends of climate warming. In this part of the Arctic, these trends are manifested by soil desiccation. It appears that slope processes depend on very local topoclimatic factors. Analysis of the obtained data with regard to palaeogeographical and climatic investigations suggests that the ice segregation forms on raised marine terraces developed during the last Holocene cooling, i.e. the Little Ice Age.  相似文献   

10.
Many parts of our planet are exposed to natural disasters such as snow avalanches, floods and earthquakes. Detailed knowledge on these natural disasters is crucial for human safety. On December 25–26, 1992, two avalanches occurred at Kayaarkası-Kastamonu in northern Turkey. The first avalanche took place at night of 25–26 December and caused no damage. The second avalanche took place at morning of 26 December, killed four people and did damage to properties. The purpose of the present study is to determine the effects of the snow avalanches on tree rings and to investigate the boundaries and velocities of the avalanches using a numerical simulation model and the tree-ring data. Increment cores from 71 trees in the avalanche-impacted area and the control site were sampled to obtain individual standard chronologies. In the analyses, trees were grouped as (1) heavily damaged by the avalanche, showing a decrease in tree-ring widths since the event, (2) trees heavily damaged by the avalanche, showing an increase in tree-ring widths a couple of years later the event and (3) trees that were not damaged by the avalanche. In this study, one of the most important results is the precise determination of the temporal and spatial patterns of the undocumented avalanche (the first avalanche) event. Avalanches were numerically simulated using dynamical avalanche simulation software ELBA+. Comparison of the simulation model with tree-ring analysis revealed valuable results about the boundaries of the zone of influence of the avalanches.  相似文献   

11.
This paper describes a rockfall event in the Daisekkei Valley of Mount Shirouma-dake (2,932 m), the northern Japanese Alps. The rockfall occurred on a steep cliff comprising well-jointed felsites and produced debris of ≥8,000 m3. Most debris was deposited on an elongated snowpatch located immediately beneath the cliff, and it caused casualties among people who were trekking along a trail on the snowpatch. Additionally, a large rock block slipped 1 km on the snowpatch. The rockfall could have been due to the differential retreat of the rockwall, which contains areas of high- and low-density joints. Seasonal and diurnal freeze–thaw activities and snow avalanches and wash appear to be important factors responsible for the retreat. Although some rock blocks that can collapse further remain on the rockwall, the position of the mountain trail in the Daisekkei Valley is fixed. Fundamental reform of tourism systems for climbers, including education on natural hazards, is required.  相似文献   

12.
Snow avalanches represent an undeniable reality in the Southern Carpathians both as a geomorphic process and as a type of hazard. Before the 1990s, few researchers focused on avalanches in Romania. However, after 1990, avalanches became an increasingly important topic of Romanian research including research on their management implications. This study focuses on the Făgăraş massif, a representative mountain unit in the Southern Carpathians that is dominant due to its glacial and periglacial relief, high altitudes and high occurrence of avalanche hazards. Three main research issues are considered. First, types of avalanches are delineated along with affected areas of the Balea glacial valley (on the northern slope) and the Capra glacial valley (on the southern slope) using data from a research centre for snow and avalanche monitoring that was created in the Balea glacial cirque in 2003. Second, the impact of avalanches on human activities is considered including transportation use of the Transfăgărăşan Highway that traverses the highest elevations in Romania and winter recreation activities such as skiing, snowboarding, climbing and hiking. The impacts on forests are also considered. Third, the needs and gaps of avalanche management are considered, specifically in the Făgăraş massif and also more generally in the mountains of Romania.  相似文献   

13.
P. Höller 《Natural Hazards》2014,71(3):1259-1288
Snow gliding is a downhill motion of snow on the ground; it is able to affect afforestation (uprooting of plants) and to cause soil erosion. Once the glide motion turns into an avalanche movement, the process is called a glide avalanche. Winters with continuing snow gliding and a high activity of glide avalanches might be called ‘glide winters’. The most recent ‘glide winter’ in the European Alps was 2011/2012. Glide avalanches have the ability to cause damage to buildings and infrastructure. This review describes the progress in research, from basic snow glide measurements via the design of sophisticated models through to comprehensive investigations concerning glide avalanche formation. However, despite the great progress made in this field of research, there are still some unsolved problems, such as the influence of soil conditions on snow gliding or the prediction of glide avalanches.  相似文献   

14.
Dendrogeomorphic research has long relied on scarred trees to reconstruct the frequency of mass‐movement processes. Injuries have mostly been dated macroscopically by counting the tree rings formed after wounding. Tree‐ring anatomical anomalies induced by cambial injury, in contrast, have only recently been recognized as proxy records of past events. We investigated 12 sub‐arctic downy birch (Betula pubescens Ehrh.) trees scarred by snow avalanches in Norway and Iceland. Earlywood vessel lumina were measured for each tree in the xylem tissue bordering the scars. Seven successive rings were examined, namely two control rings laid down prior to wounding and five rings in the wound xylem. We provide evidence that snow‐avalanche‐induced wounding resulted in atypically narrow earlywood vessels over at least two years. Our data demonstrate that wound‐associated vessel anomalies represent tangible markers of mass‐movement processes, and as such make a viable tool for reconstructing past events. Similar dendrogeomorphic studies based on tree‐ring anatomy can be readily conducted with other mass‐movement processes, as well as with other broad‐leaved tree species. Ultimately, this new approach will foster increment coring over more invasive sampling techniques.  相似文献   

15.
During the last 50 years, an average of 30 persons per year was killed by avalanches in Austria. About one-third of all avalanche fatalities occurred as a result of so-called ‘catastrophic avalanches’. ‘Catastrophic avalanches’ are spontaneously released avalanches that affect villages and cause damage to property (buildings, roads and other infrastructure). The biggest avalanche events in Austria were in 1950/1951 (135 fatalities), in 1953/1954 (143 fatalities) and in February 1999, when 38 persons were killed in Galtür and Valzur. This article deals with an analysis of nine major avalanche cycles in the last 55 years. An avalanche cycle in this article is defined as 50 recorded avalanches of at least size 3 in two days and/or 5 persons killed in villages within two days. The basis of this study are the well-documented records from Fliri (1998), who analysed natural disasters in the western part of Austria and the Trentino, including floods, mudflows, earthquakes and avalanches. The meteorological data were taken from two relevant observation sites in the northern part of the Austrian Alps, from two sites in an intermediate and continental region, respectively and from one site in the southern part of the Austrian Alps. Atmospheric patterns were analysed by using weather charts for the relevant periods. Both the meteorological data and the weather charts were provided by the Central Institute for Meteorology and Geodynamics (ZAMG). It was found that there was a major cycle every 6 years (on average). Two-thirds of all investigated cycles were characterised by a continuous increase of snow depth over a period of at least three days. In only three periods (1975, 1986, 1988), daily extreme values could be observed. More than 40% of all the cycles occurred in January. In two-thirds, a north-westerly oriented frontal zone was responsible for the formation of a major cycle. The remaining cycles were released by low-pressure areas over Central Europe and the Mediterranean Sea, respectively.  相似文献   

16.
Barbolini  M.  Natale  L.  Savi  F. 《Natural Hazards》2002,25(3):225-244
Dynamical models for calculating snow avalanche motion have gained growingimportance in recent years for avalanche hazard assessment. Nevertheless, inherentuncertainties in their input-data specification, although well acknowledged, areusually not explicitly incorporated into the analysis and considered in the mappingresults. In particular, the estimate of avalanche release conditions is affected bystrong uncertainties when associated to a return period. These sources of error arenormally addressed through sensitivity analysis or conservative parameters estimate.However, each of these approaches has limitations in assessing the statistical implications of uncertainties.In the present paper the problem of release scenarios randomness is looked at following a Monte Carlo procedure. This statistical sampling-analysis method allows the evaluation of the probability distributions of relevant variables for avalanche hazard assessment – such as runout distance and impact pressure – once the release variables – essentially releasedepth and release length – are expressed in terms of probability distributions, accounting explicitly for inherent uncertainties in their definition. Both the theoretical framework of this procedure and its application to a real study case are presented. As initial step of this research in the present work the attention is mainly focused on flowing avalanches descending on open slopes. Therefore, the one-dimensional version of VARA dynamic models is usedfor avalanche simulations.  相似文献   

17.
Due to its geographical location, geology and topography, Turkey mainly undergoes three different types of natural disasters related to gravity flows. They are floods, landslides and snow avalanches.The heavy snow falls during winter pose the hazard of snow avalanches. According to statistics, 800 people were killed in snow avalanches during the period of 1960–1997. Within the program of the International Decade of Natural Disaster Reduction (1990–2000), an international cooperation has been initiated among SFISAR (Swiss Federal Institute for Snow and Avalanche Research), CEMAGREF (Centre National du Machinisme Agricole du Génie Rural des Eaux at des Forets) and AFET (Turkish Ministry of Public Works and Settlement, General Directorate of Disaster Affairs). This three-year project started in 1994 as a development project on avalanche forecasting, mapping, zoning and paravalanche construction technologies. For the pilot project area, the Soanli Mountains located in north-eastern Turkey were chosen, covering an area of approximately 40 by 30 km. After training the Turkish engineers, the basic technologies in avalanche forecasting and avalanche mapping were transferred from Switzerland and France to Turkey with the necessary infrastructure. The difficulties faced in meteorological data collection with the help of local observers and the limited data available caused some delay in avalanche forecasting. If automatic weather stations could take the place of manual work, the realization of a prognosis would be quicker. At present, avalanche-hit houses are rebuilt in new disaster-free zones by AFET. With this project, the idea of using paravalanche structures for protection is promoted. The physico-sociological impacts of avalanche disasters, avalanche mapping and zoning of disaster areas on local people are also studied.  相似文献   

18.
This paper focuses on the structural glaciology, dynamics, debris transport paths and sedimentology of the forefield of Soler Glacier, a temperate outlet glacier of the North Patagonian Icefield in southern Chile. The glacier is fed by an icefall from the icefield and by snow and ice avalanches from surrounding mountain slopes. The dominant structures in the glacier are ogives, crevasses and crevasse traces. Thrusts and recumbent folds are developed where the glacier encounters a reverse slope, elevating basal and englacial material to the ice surface. Other debris sources for the glacier include avalanche and rockfall material, some of which is ingested in marginal crevasses. Debris incorporated in the ice and on its surface controls both the distribution of sedimentary facies on the forefield and moraine ridge morphology. Lithofacies in moraine ridges on the glacier forefield include large isolated boulders, diamictons, gravel, sand and fine-grained facies. In relative abundance terms, the dominant lithofacies and their interpretation are sandy boulder gravel (ice-marginal), sandy gravel (glaciofluvial), angular gravel (supraglacial) and diamicton (basal glacial). Proglacial water bodies are currently developing between the receding glacier and its frontal and lateral moraines. The presence of folded sand and laminites in moraine ridges in front of the glacier suggests that, during a previous advance, Soler Glacier over-rode a former proglacial lake, reworking lacustrine deposits. Post-depositional modification of the landform/sediment assemblage includes melting of the ice-core beneath the sediment cover, redistribution of finer material across the proglacial area by aeolian processes and fluvial reworking. Overall, the preservation potential of this landform/sediment assemblage is high on the centennial to millennial timescale.  相似文献   

19.
Avalanche hazard and risk mapping is of utmost importance in mountain areas in Europe and elsewhere. Advanced methods have been developed to describe several aspects of avalanche hazard assessment, such as the dynamics of snow avalanches or the intensity of snowfall to assume as a reference meteorological forcing. However, relatively little research has been conducted on the identification of potential avalanche release areas. In this paper, we present a probabilistic assessment of potential avalanche release areas in the Italian Autonomous Province of Bolzano, eastern Alps, using the Weights of Evidence and Logistic Regression methods with commonly available GIS datasets. We show that a data-driven statistical model performs better than simple, although widely adopted, screening criteria that were proposed in the past, although the complexity of observed release areas is only partly captured by the model. In the best case, the model enables predicting about 70 % of avalanches in the 20 % of area classified at highest hazard. Based on our results, we suggest that probabilistic identification of potential release areas could provide a useful aid in the screening of sites for subsequent, more detailed hazard assessment.  相似文献   

20.
A large rock and ice avalanche occurred on the north face of Mount Steele, southwest Yukon Territory, Canada, on July 24, 2007. In the days and weeks preceding the landslide, several smaller avalanches initiated from the same slope. The ice and rock debris traveled a maximum horizontal distance 5.76 km with a maximum vertical descent of 2,160 m, leaving a deposit 3.66 km2 in area on Steele Glacier. The seismic magnitude estimated from long-period surface waves (M s) is 5.2. Modeling of the waveforms suggests an estimated duration of approximately 100 s and an average velocity of between 35 and 65 m/s. This landslide is one of 18 large rock avalanches known to have occurred since 1899 on slopes adjacent to glaciers in western Canada. We describe the setting, reconstruct the event chronology and present a preliminary characterization of the Mount Steele ice and rock avalanches based on field reconnaissance, analysis of seismic records and an airborne LiDAR survey. We also present the results of a successful dynamic simulation for the July 24 event.  相似文献   

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