To see the other types of publications on this topic, follow the link: Avalanches Avalanches.
Journal articles on the topic 'Avalanches Avalanches'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Avalanches Avalanches.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Bartelt, P., and V. Stöckli. "The influence of tree and branch fracture, overturning and debris entrainment on snow avalanche flow." Annals of Glaciology 32 (2001): 209–16. http://dx.doi.org/10.3189/172756401781819544.
Full textAbstract:
AbstractA simple center-of-mass avalanche model that accounts for avalanche flow in forests is presented. The model applies the principle of conservation of energy to calculate the deceleration of avalanches caused by tree fracture, overturning and debris entrainment. The model relates the physical properties of forests (tree spacing, tree age, tree type, soil conditions) to avalanche flow. Modified dry-Coulomb and velocity-dependent friction parameters commonly used in avalanche runout calculations are derived. Example calculations demonstrate how the model can be applied to back-calculate observed avalanche events. The model quantitatively explains why large avalanches can destroy forests without significant deceleration. Furthermore, it shows why tree fracture consume/little of the avalanche’s energy. Finally, the model reveals how protective forests in avalanche tracks can be maintained over time to provide the best protective capacity against snow avalanches.
2
Buisson, Laurent, and Claude Charlier. "Avalanche modelling and integration of expert knowledge in the ELSA system." Annals of Glaciology 18 (1993): 123–28. http://dx.doi.org/10.1017/s026030550001137x.
Full textAbstract:
The choice of the best protection system against avalanches on a particular path requires an accurate description, or image, of these avalanches. In order to get this image, avalanche consultants can use several numerical models which are often difficult to handle. Moreover, these models deal only with a part of the phenomena involved in avalanches and ignore the others. As a result, the consultants must use their experience and knowledge to imagine the avalanches on any particular path. This paper presents ELSA (Etude et Limites de Sites Avalancheux), a computer system dedicated to the modelling of the knowledge of avalanche experts and to the integration of the new symbolic computer models with the classical numerical models. The basic aim of integration is to build a unique computer system incorporating all these models. After a description of the terrain representation, we present the different scenarios that ELSA takes into account. Then, the methods which deal with some phenomena occurring in avalanches are described. The problems involved in the integration of these methods close this paper.
3
Buisson, Laurent, and Claude Charlier. "Avalanche modelling and integration of expert knowledge in the ELSA system." Annals of Glaciology 18 (1993): 123–28. http://dx.doi.org/10.3189/s026030550001137x.
Full textAbstract:
The choice of the best protection system against avalanches on a particular path requires an accurate description, or image, of these avalanches. In order to get this image, avalanche consultants can use several numerical models which are often difficult to handle. Moreover, these models deal only with a part of the phenomena involved in avalanches and ignore the others. As a result, the consultants must use their experience and knowledge to imagine the avalanches on any particular path.This paper presents ELSA (Etude et Limites de Sites Avalancheux), a computer system dedicated to the modelling of the knowledge of avalanche experts and to the integration of the new symbolic computer models with the classical numerical models. The basic aim of integration is to build a unique computer system incorporating all these models.After a description of the terrain representation, we present the different scenarios that ELSA takes into account. Then, the methods which deal with some phenomena occurring in avalanches are described. The problems involved in the integration of these methods close this paper.
4
Fukushima, Yusuke, and Norio Hayakawa. "Analysis of powder-snow avalanches using three-dimensional topographic data." Annals of Glaciology 18 (1993): 102–6. http://dx.doi.org/10.1017/s0260305500011332.
Full textAbstract:
A fluid-dynamical model of powder-snow avalanches is developed which takes into account three-dimensional topography and can compute an avalanche’s running course. The model also predicts the variations of height, speed and concentration of snow particles in the avalanche, as well as the level of turbulence. Application of the model to the Maseguchi avalanche, which occurred in 1986 at Niigata, Japan, shows it can provide reasonable prediction of the running course, height and speed of an avalanche.
5
Fukushima, Yusuke, and Norio Hayakawa. "Analysis of powder-snow avalanches using three-dimensional topographic data." Annals of Glaciology 18 (1993): 102–6. http://dx.doi.org/10.3189/s0260305500011332.
Full textAbstract:
A fluid-dynamical model of powder-snow avalanches is developed which takes into account three-dimensional topography and can compute an avalanche’s running course. The model also predicts the variations of height, speed and concentration of snow particles in the avalanche, as well as the level of turbulence. Application of the model to the Maseguchi avalanche, which occurred in 1986 at Niigata, Japan, shows it can provide reasonable prediction of the running course, height and speed of an avalanche.
6
Keylock, Chris. "Snow avalanches." Progress in Physical Geography: Earth and Environment 21, no. 4 (December 1997): 481–500. http://dx.doi.org/10.1177/030913339702100401.
Full textAbstract:
Snow avalanches have a substantial impact upon human activity in mountainous regions. In this article I employ a climatological framework to examine the mechanisms by which snow avalanches occur. This is followed by a discussion of the hydrologic and geomorphic aspects of avalanches, and an examination of the current state of research as regards predicting maximum avalanche runout and avalanche risk. It is hoped that this article brings to the reader's attention the wide range of literature that focuses upon this very hazardous natural phenomenon.
7
Schweizer, Jürg, Christoph Mitterer, Frank Techel, Andreas Stoffel, and Benjamin Reuter. "On the relation between avalanche occurrence and avalanche danger level." Cryosphere 14, no. 2 (March 2, 2020): 737–50. http://dx.doi.org/10.5194/tc-14-737-2020.
Full textAbstract:
Abstract. In many countries with seasonally snow-covered mountain ranges warnings are issued to alert the public about imminent avalanche danger, mostly employing an ordinal, five-level danger scale. However, as avalanche danger cannot be measured, the characterization of avalanche danger remains qualitative. The probability of avalanche occurrence in combination with the expected avalanche type and size decide on the degree of danger in a given forecast region (≳100 km2). To describe avalanche occurrence probability, the snowpack stability and its spatial distribution need to be assessed. To quantify the relation between avalanche occurrence and avalanche danger level, we analyzed a large data set of visually observed avalanches (13 918 in total) from the region of Davos (eastern Swiss Alps, ∼300 km2), all with mapped outlines, and we compared the avalanche activity to the forecast danger level on the day of occurrence (3533 danger ratings). The number of avalanches per day strongly increased with increasing danger level, confirming that not only the release probability but also the frequency of locations with a weakness in the snowpack where avalanches may initiate from increase within a region. Avalanche size did not generally increase with increasing avalanche danger level, suggesting that avalanche size may be of secondary importance compared to snowpack stability and its distribution when assessing the danger level. Moreover, the frequency of wet-snow avalanches was found to be higher than the frequency of dry-snow avalanches for a given day and danger level; also, wet-snow avalanches tended to be larger. This finding may indicate that the danger scale is not used consistently with regard to avalanche type. Even though observed avalanche occurrence and avalanche danger level are subject to uncertainties, our findings on the characteristics of avalanche activity suggest reworking the definitions of the European avalanche danger scale. The description of the danger levels can be improved, in particular by quantifying some of the many proportional quantifiers. For instance, based on our analyses, “many avalanches”, expected at danger level 4-High, means on the order of at least 10 avalanches per 100 km2. Whereas our data set is one of the most comprehensive, visually observed avalanche records are known to be inherently incomplete so that our results often refer to a lower limit and should be confirmed using other similarly comprehensive data sets.
8
McClung, D. M. "The effects of El Niño and La Niña on snow and avalanche patterns in British Columbia, Canada, and central Chile." Journal of Glaciology 59, no. 216 (2013): 783–92. http://dx.doi.org/10.3189/2013jog12j192.
Full textAbstract:
AbstractEl Niño and La Niña affect global climate and atmospheric circulation to determine winter temperature and precipitation patterns. Both winter temperatures and the associated precipitation patterns have effects on mountain snow deposition and snow avalanche occurrences. Approximately 25 000 slab avalanches from 30 winters were analyzed in relation to snowfall patterns contrasted for El Niño and La Niña winters for two avalanche areas with different snow climates in British Columbia (BC), Canada. La Niña winters were shown to produce more snow, more avalanches and a higher percentage of dry avalanches than wet avalanches. The data and analysis show that the avalanche patterns depend on the altitude and snow climate. Analysis of snowfall and accident data from the Andes of Chile suggests behavior opposite to BC. El Niño winters in central Chile produced the most snow and, by inference, the most avalanches. This paper is the first to show the links of El Niño and La Niña to snow avalanche activity.
9
Maggioni, Margherita, Monica Barbero, Fabrizio Barpi, Mauro Borri-Brunetto, Valerio De Biagi, Michele Freppaz, Barbara Frigo, Oronzo Pallara, and Bernardino Chiaia. "Snow Avalanche Impact Measurements at the Seehore Test Site in Aosta Valley (NW Italian Alps)." Geosciences 9, no. 11 (November 7, 2019): 471. http://dx.doi.org/10.3390/geosciences9110471.
Full textAbstract:
In full-scale snow avalanche test sites, structures such as pylons, plates, or dams have been used to measure impact forces and pressures from avalanches. Impact pressures are of extreme importance when dealing with issues such as hazard mapping and the design of buildings exposed to avalanches. In this paper, we present the force measurements recorded for five selected avalanches that occurred at the Seehore test site in Aosta Valley (NW Italian Alps). The five avalanches were small to medium-sized and cover a wide range in terms of snow characteristics and flow dynamics. Our aim was to analyze the force and pressure measurements with respect to the avalanche characteristics. We measured pressures in the range of 2 to 30 kPa. Though without exhaustive measurements of the avalanche flows, we found indications of different flow regimes. For example, we could appreciate some differences in the vertical profile of the pressures recorded for wet dense avalanches and powder ones. Being aware of the fact that more complete measurements are necessary to fully describe the avalanche flows, we think that the data of the five avalanches triggered at the Seehore test site might add some useful information to the ongoing scientific discussion on avalanche flow regimes and impact pressure.
10
Shahverdian, A. Yu. "Lattice Animals and Self-Organized Criticality." Fractals 05, no. 02 (June 1997): 199–213. http://dx.doi.org/10.1142/s0218348x9700019x.
Full textAbstract:
The paper considers one model of SOC close to BTW and slider blocks models. In addition, it introduces an additional time parameter and imposes special restrictions on the avalanche geometrical structure. The generalization and modification of the avalanche's concept allows us to apply H. Weyl's theorem in the dynamical system theory so as to obtain the strong and exact results in this area. We introduce some combinatorial characteristic of clusters and use it as a tool for estimating the frequency of the avalanches. The results obtained give the asymptotically exact expressions for the asymptotical frequency as well as two special types of such extended avalanches. In some special cases, they reduce the determination of the frequency of the avalanches to combinatorial enumerative problem for lattice animals on the d-dimensional torus. The other two results are related to the one-dimensional model and establish the connection between the SOC and the theory of number partitions.
11
Haraldsdóttir, Svanbjörg H., Haraldur Ólafsson, Yves Durand, Gerald Giraud, and Laurent Mérindol. "A system for prediction of avalanche hazard in the windy climate of Iceland." Annals of Glaciology 38 (2004): 319–24. http://dx.doi.org/10.3189/172756404781815293.
Full textAbstract:
AbstractA system for predicting avalanche hazard in the windy climate of Vestfirðir, northwest Iceland, is presented. The system is based on (a) numerical simulations of the snowpack and evaluation of avalanche hazard due to overloading by the snow models SAFRAN–Crocus and MÉPRA, and (b) observations of wind speed in the mountains used as a proxy for snowdrift. The system was tested during two winter seasons and correctly predicts 30 out of 35 avalanche days. The 5 missing days feature either large spatial gradients in precipitation or very strong winds a few days before the avalanches, indicating much snowdrift. A comparison of the simulated avalanche hazard and observations of avalanches confirms that snowdrift is of primary importance not only for large avalanches, as already established, but also for small and medium-size avalanches in Vestfirðir. The system is a first step towards an objective evaluation of avalanche hazard in Iceland.
12
Anderson, G., and D. McClung. "Snow avalanche penetration into mature forest from timber-harvested terrain." Canadian Geotechnical Journal 49, no. 4 (April 2012): 477–84. http://dx.doi.org/10.1139/t2012-018.
Full textAbstract:
Clear-cut logging in British Columbia, Canada, is creating new avalanche start zones from which snow avalanches sufficient in size to penetrate and destroy mature forest cover can initiate. In addition to creating new start zones, the presence of these logging cut blocks can augment the destructive potential of previously existing avalanche paths. Forest-penetrating avalanches can pose a significant risk to down-slope structures and resources. This study is the first to develop and utilize a database containing information on penetration distances and lateral spread from avalanches that have penetrated forest cover. The study area for this research spans the Southern Coast and Columbia Mountains of British Columbia, Canada. Analysis focuses on terrain characteristics related to forest penetration and the resultant destruction of mature standing forest. Physical terrain and vegetation characteristics in the avalanche starting zone, track, and runout zone of 45 forest-penetrating avalanches are described, measured, and parameterized. The results provide tools to assess and evaluate potential forest-penetrating avalanche terrain, and runout models for avalanches in forested terrain.
13
Fujisawa, K., R. Tsunaki, and I. Kamiishi. "Estimating snow avalanche runout distances from topographic data." Annals of Glaciology 18 (1993): 239–44. http://dx.doi.org/10.1017/s0260305500011587.
Full textAbstract:
To protect rural areas and roads from disasters caused by snow avalanches, avalanche hazard maps are being developed. In Japan, when determining snow avalanche runout distances, empirical values are normally used. These assume that the line-of-sight angle at the starting point of an avalanche, viewed from its runout point, is less than 18° for surface-layer avalanches and less than 24° for full-depth layer avalanches. This rule of thumb ignores topographic features of the slope carrying the large mass of snow. We have made analyses to find a method that can obtain the avalanche runout distance, taking into consideration the longitudinal profiles of the sites, using regression analyses on data from 66 avalanches. The line-of-sight angle can be expressed sufficiently by functions, such as line-of-sight angle between the starting point of an avalanche and a point on its course of flow 10° in gradient, an angle at the starting point of an avalanche, and the curvature of an approximate quadratic curve of topography. Based on statistics for the above relationship, we have established four different ranking categories to classify the degree of hazard. If the starting points of avalanches are known, hazardous areas can automatically be ranked on a basis of topographic data.
14
Fujisawa, K., R. Tsunaki, and I. Kamiishi. "Estimating snow avalanche runout distances from topographic data." Annals of Glaciology 18 (1993): 239–44. http://dx.doi.org/10.3189/s0260305500011587.
Full textAbstract:
To protect rural areas and roads from disasters caused by snow avalanches, avalanche hazard maps are being developed. In Japan, when determining snow avalanche runout distances, empirical values are normally used. These assume that the line-of-sight angle at the starting point of an avalanche, viewed from its runout point, is less than 18° for surface-layer avalanches and less than 24° for full-depth layer avalanches. This rule of thumb ignores topographic features of the slope carrying the large mass of snow. We have made analyses to find a method that can obtain the avalanche runout distance, taking into consideration the longitudinal profiles of the sites, using regression analyses on data from 66 avalanches. The line-of-sight angle can be expressed sufficiently by functions, such as line-of-sight angle between the starting point of an avalanche and a point on its course of flow 10° in gradient, an angle at the starting point of an avalanche, and the curvature of an approximate quadratic curve of topography. Based on statistics for the above relationship, we have established four different ranking categories to classify the degree of hazard. If the starting points of avalanches are known, hazardous areas can automatically be ranked on a basis of topographic data.
15
Takeuchi, Yukari, Koichi Nishimura, and Abani Patra. "Observations and numerical simulations of the braking effect of forests on large-scale avalanches." Annals of Glaciology 59, no. 77 (November 28, 2018): 50–58. http://dx.doi.org/10.1017/aog.2018.22.
Full textAbstract:
ABSTRACTAlthough the disaster reduction effects of forest braking have long been known empirically, they have not been known in detail down to recent. In this study, we ascertained forest braking effect by numerical simulations using the avalanche dynamics program, TITAN2D, to model large-scale avalanches. One of these avalanches occurred in the Makunosawa valley, Myoko, and damaged a cedar forest; the others occurred on Mt. Iwate and damaged a subalpine forest. All avalanches damaged many trees and terminated within the forests. In our simulations, the resistance of the forests to avalanches is simulated using a larger bed friction angle. Fitting the observations from the Makunosawa avalanche by trial and error, a bed friction angle of 13–14° in the non-forested area and of 25° in the forested area is obtained. We conducted simulations of the Mt. Iwate avalanches using the same method as for the Makunosawa valley avalanche, and obtained good agreement between observations and simulations. Simulations reveal that without the forest, the avalanche would have traveled at least 200 m farther than the forest's actual end in the Makunosawa valley, and at least 200 m and possibly up to 600 m farther on Mt. Iwate. This study therefore clearly shows that forests provide a braking effect for avalanches.
16
Yanlong, Wang, and Huang Maohuan. "An outline of avalanches in the southeastern Tibet Plateau, China." Annals of Glaciology 16 (1992): 146–50. http://dx.doi.org/10.3189/1992aog16-1-146-150.
Full textAbstract:
Avalanches are a widespread hazard that cause serious damage in the southeastern Tibetan Plateau. Abundant solid precipitation and high relief are favourable for avalanche occurrence. The monsoon climate brings a lot of precipitation which, however, is not well distributed. Avalanches are most common around the margins of the plateau. Wet snow avalanches occur most frequently. Based on data on precipitation and topographical relief, a map is drawn showing the areal distribution of avalanche hazards.
17
Yanlong, Wang, and Huang Maohuan. "An outline of avalanches in the southeastern Tibet Plateau, China." Annals of Glaciology 16 (1992): 146–50. http://dx.doi.org/10.1017/s0260305500004973.
Full textAbstract:
Avalanches are a widespread hazard that cause serious damage in the southeastern Tibetan Plateau. Abundant solid precipitation and high relief are favourable for avalanche occurrence. The monsoon climate brings a lot of precipitation which, however, is not well distributed. Avalanches are most common around the margins of the plateau. Wet snow avalanches occur most frequently. Based on data on precipitation and topographical relief, a map is drawn showing the areal distribution of avalanche hazards.
18
Sovilla, B., I. Sonatore, Y. Bühler, and S. Margreth. "Wet-snow avalanche interaction with a deflecting dam: field observations and numerical simulations in a case study." Natural Hazards and Earth System Sciences 12, no. 5 (May 11, 2012): 1407–23. http://dx.doi.org/10.5194/nhess-12-1407-2012.
Full textAbstract:
Abstract. In avalanche-prone areas, deflecting dams are widely used to divert avalanches away from endangered objects. In recent years, their effectiveness has been questioned when several large and multiple avalanches have overrun such dams. In 2008, we were able to observe a large wet-snow avalanche, characterized by an high water content, that interacted with a deflecting dam and overflowed it at its lower end. To evaluate the dam's performance, we carried out an airborne laser scanning campaign immediately after the avalanche. This data, together with a video sequence made during the avalanche descent, provided a unique data set to study the dynamics of a wet dense snow avalanche and its flow behavior along a deflecting dam. To evaluate the effect of the complex flow field of the avalanche along the dam and to provide a basis for discussion of the residual risk, we performed numerical simulations using a two-dimensional dense snow avalanche dynamics model with entrainment. In comparison to dry dense snow avalanches, we found that wet-snow avalanches, with high water content, seem to be differently influenced by the local small-scale topography roughness. Rough terrain close to the dam deflected the flow to produce abrupt impacts with the dam. At the impact sites, instability waves were generated and increased the already large flow depths. The complex flow dynamics around the dam may produce large, local snow deposits. Furthermore, the high water content in the snow may decrease the avalanche internal friction angle, inducing wet-snow avalanches to spread further laterally than dry-snow avalanches. Based on our analysis, we made recommendations for designing deflecting dams and for residual risk analysis to take into account the effects of wet-snow avalanche flow.
19
Yang, Jinming, Chengzhi Li, Lanhai Li, Jianli Ding, Run Zhang, Tao Han, and Yang Liu. "Automatic Detection of Regional Snow Avalanches with Scattering and Interference of C-band SAR Data." Remote Sensing 12, no. 17 (August 27, 2020): 2781. http://dx.doi.org/10.3390/rs12172781.
Full textAbstract:
Avalanche disasters are extremely destructive and catastrophic, often causing serious casualties, economic losses and surface erosion. However, far too little attention has been paid to utilizing remote sensing mapping avalanches quickly and automatically to mitigate calamity. Such endeavors are limited by formidable natural conditions, human subjective judgement and insufficient understanding of avalanches, so they have been incomplete and inaccurate. This paper presents an objective and widely serviceable method for regional auto-detection using the scattering and interference characteristics of avalanches extracted from Sentinel-1 SLC images. Six indices are established to distinguish avalanches from surrounding undisturbed snow. The active avalanche belts in Kizilkeya and Aktep of the Western TianShan Mountains in China lend urgency to this research. Implementation found that smaller avalanches can be consistently identified more accurately in descending images. Specifically, 281 and 311 avalanches were detected in the ascending and descending of Kizilkeya, respectively. The corresponding numbers on Aktep are 104 and 114, respectively. The resolution area of single avalanche detection can reach 0.09 km2. The performance of the model was excellent in all cases (areas under the curve are 0.831 and 0.940 in descending and ascending of Kizilkeya, respectively; and 0.807 and 0.938 of Aktep, respectively). Overall, the evaluation of statistical indices are POD > 0.75, FAR < 0.34, FOM < 0.13 and TSS > 0.75. The results indicate that the performance of the innovation proposed in this paper, which employs multivariate comprehensive descriptions of avalanche characteristics to actualize regional automatic detection, can be more objective, accurate, applicable and robust to a certain extent. The latest and more complete avalanche inventory generated by this design can effectively assist in addressing the increasingly severe avalanche disasters and improving public awareness of avalanches in alpine areas.
20
Marchetti, E., M. Ripepe, G. Ulivieri, and A. Kogelnig. "Infrasound array criteria for automatic detection and front velocity estimation of snow avalanches: towards a real-time early-warning system." Natural Hazards and Earth System Sciences 15, no. 11 (November 30, 2015): 2545–55. http://dx.doi.org/10.5194/nhess-15-2545-2015.
Full textAbstract:
Abstract. Avalanche risk management is strongly related to the ability to identify and timely report the occurrence of snow avalanches. Infrasound has been applied to avalanche research and monitoring for the last 20 years but it never turned into an operational tool to identify clear signals related to avalanches. We present here a method based on the analysis of infrasound signals recorded by a small aperture array in Ischgl (Austria), which provides a significant improvement to overcome this limit. The method is based on array-derived wave parameters, such as back azimuth and apparent velocity. The method defines threshold criteria for automatic avalanche identification by considering avalanches as a moving source of infrasound. We validate the efficiency of the automatic infrasound detection with continuous observations with Doppler radar and we show how the velocity of a snow avalanche in any given path around the array can be efficiently derived. Our results indicate that a proper infrasound array analysis allows a robust, real-time, remote detection of snow avalanches that is able to provide the number and the time of occurrence of snow avalanches occurring all around the array, which represent key information for a proper validation of avalanche forecast models and risk management in a given area.
21
Patten, Robin, and Dennis Knight. "Snow Avalanches and Vegetation Pattern in Cascade Canyon, Grand Teton National Park." UW National Parks Service Research Station Annual Reports 10 (January 1, 1986): 104–19. http://dx.doi.org/10.13001/uwnpsrc.1986.2565.
Full textAbstract:
Snow avalanches are an important factor in the landscape of Cascade Canyon, influencing both the vegetation types and their distribution. The relationship between avalanches and vegetation is most apparent in the conifer woodlands. Large-conifer woodlands are found primarily outside of avalanche areas while essentially all of the Small-conifer woodlands are within avalanche areas. This suggests that Small-conifer woodlands are created and maintained by avalanches. Slope aspect is also important in the vegetation pattern of Cascade Canyon. Environmental conditions resulting from the aspect of the slope affect vegetation distributions and potentially reduce the importance of avalanches in structuring vegetation patterns, especially on the south-facing slope.
22
Bessason, Bjarni, Gísli Eiríksson, Óðinn Thorarinsson, Andrés Thórarinsson, and Sigurður Einarsson. "Automatic detection of avalanches and debris flows by seismic methods." Journal of Glaciology 53, no. 182 (2007): 461–72. http://dx.doi.org/10.3189/002214307783258468.
Full textAbstract:
AbstractThe road along the Óshlíð hillside in the West Fjords region of Iceland is one of the most hazardous roads in Iceland due to avalanches, rockfalls and debris flows. The road has little traffic, but nevertheless traffic accidents caused by the severe conditions at the site are common. A number of avalanche tracks are found on the hillside. In some of these tracks, avalanches occur more frequently than in others. When there is an avalanche threat, avalanches generally flow over many tracks in a short time. Monitoring vibrations in the tracks with the highest avalanche frequency can indicate when avalanches start flowing down the hillside in a snowstorm, and avalanche hazard can then be declared with the specific site indicated. The same methodology can be used for rockfalls and debris flows, which are strongly affected by weather conditions and typically occur in clusters. Based on this knowledge, a research project was initiated in February 1996 with the objective of developing an automatic system based on seismic measurements to detect and analyze avalanches on the Óshlíð hillside and to instantly send a warning to a control station.
23
Muntán, Elena, Laia Andreu, Pere Oller, Emilia Gutiérrez, and Pere Martínez. "Dendrochronological study of the Canal del Roc Roig avalanche path: first results of the Aludex project in the Pyrenees." Annals of Glaciology 38 (2004): 173–79. http://dx.doi.org/10.3189/172756404781815077.
Full textAbstract:
AbstractHistorical data about ancient avalanches are scarce in the Pyrenees. Dendrochronology can provide new data about past avalanches and their return period, but up to now little research has been carried out with this purpose. The Aludex project aims to obtain information about the frequency and extent of extreme avalanches, using a dendrochronological and a nivo-meteorological approach. In this paper, we present the results of a dendrochronological study of the Canal del Roc Roig avalanche path which was affected by two extreme avalanches in February 1996. This first dendrochronological study has permitted us to assess the tree-ring signals due to avalanche events in 53 out of 132 dated trees. The trees presented a variety of responses to the 1996 avalanche events. It is shown that the type of tree-ring signal depends on tree age. The methodology has proved successful in detecting the 1996 and 1972 documented avalanche events, and provided outstanding evidence of undocumented past events such as one in 1930.
24
Marchetti, E., M. Ripepe, G. Ulivieri, and A. Kogelnig. "Infrasound array criteria for automatic detection and front velocity estimation of snow avalanches: towards a real-time early-warning system." Natural Hazards and Earth System Sciences Discussions 3, no. 4 (April 17, 2015): 2709–37. http://dx.doi.org/10.5194/nhessd-3-2709-2015.
Full textAbstract:
Abstract. Avalanche risk management is strongly related to the ability to identify and timely report the occurrence of snow avalanches. Infrasound has been applied to avalanche research and monitoring for the last 20 years but it never turned into an operational tool for the ambiguity to identify clear signals related to avalanches. We present here a new method based on the analysis of infrasound signals recorded by a small aperture array in Ischgl (Austria), which overcome now this limit. The method is based on array derived wave parameters, such as back-azimuth and apparent velocity. The method defines threshold criteria for automatic avalanche identification considering avalanches as a moving source of infrasound. We validate efficiency of the automatic infrasound detection with continuous observations with Doppler Radar and we show how dynamics parameters such as the velocity of a snow avalanche in any given path around the array can be efficiently derived. Our results indicate that a proper infrasound array analysis allows a robust, real-time, remote detection of snow avalanches that could thus contribute significantly to avalanche forecast and risk management.
25
Lato, M. J., R. Frauenfelder, and Y. Bühler. "Automated detection of snow avalanche deposits: segmentation and classification of optical remote sensing imagery." Natural Hazards and Earth System Sciences 12, no. 9 (September 13, 2012): 2893–906. http://dx.doi.org/10.5194/nhess-12-2893-2012.
Full textAbstract:
Abstract. Snow avalanches in mountainous areas pose a significant threat to infrastructure (roads, railways, energy transmission corridors), personal property (homes) and recreational areas as well as for lives of people living and moving in alpine terrain. The impacts of snow avalanches range from delays and financial loss through road and railway closures, destruction of property and infrastructure, to loss of life. Avalanche warnings today are mainly based on meteorological information, snow pack information, field observations, historically recorded avalanche events as well as experience and expert knowledge. The ability to automatically identify snow avalanches using Very High Resolution (VHR) optical remote sensing imagery has the potential to assist in the development of accurate, spatially widespread, detailed maps of zones prone to avalanches as well as to build up data bases of past avalanche events in poorly accessible regions. This would provide decision makers with improved knowledge of the frequency and size distributions of avalanches in such areas. We used an object–oriented image interpretation approach, which employs segmentation and classification methodologies, to detect recent snow avalanche deposits within VHR panchromatic optical remote sensing imagery. This produces avalanche deposit maps, which can be integrated with other spatial mapping and terrain data. The object-oriented approach has been tested and validated against manually generated maps in which avalanches are visually recognized and digitized. The accuracy (both users and producers) are over 0.9 with errors of commission less than 0.05. Future research is directed to widespread testing of the algorithm on data generated by various sensors and improvement of the algorithm in high noise regions as well as the mapping of avalanche paths alongside their deposits.
26
Eglit, Margarita, Alexander Yakubenko, and Julia Zayko. "A Review of Russian Snow Avalanche Models—From Analytical Solutions to Novel 3D Models." Geosciences 10, no. 2 (February 20, 2020): 77. http://dx.doi.org/10.3390/geosciences10020077.
Full textAbstract:
The article is a review of mathematical models of snow avalanches that have been proposed since the middle of the 20th century and are still in use. The main attention is paid to the work of researchers from the Soviet Union and Russia, since many of their works were published only in Russian and are not widely available. Mathematical models of various levels of complexity for avalanches of various types—from dense to powder-snow avalanches—are discussed. Analytical solutions including formulas for the avalanche front speed are described. The results of simulations of the movement of avalanches are given that were used to create avalanche hazard maps. The last part of the article is devoted to constructing models of a new type, in which avalanches are considered as laminar or turbulent flows of non-Newtonian fluids, using the full (not depth-averaged) equations of continuum mechanics. The results of a numerical study of the effect of non-Newtonian rheology and mass entrainment on the avalanche dynamics are presented.
27
Vera Valero, C., Y. Bühler, and P. Bartelt. "Point release wet snow avalanches." Natural Hazards and Earth System Sciences Discussions 3, no. 4 (April 30, 2015): 2883–912. http://dx.doi.org/10.5194/nhessd-3-2883-2015.
Full textAbstract:
Abstract. Wet snow avalanches can initiate from large fracture slabs or small point releases. Point release wet snow avalanches can reach dangerous proportions when they (1) initiate on steep and long avalanche paths and (2) entrain warm moist snow. In this paper we investigate the dynamics of point release wet snow avalanches by applying a numerical model to simulate documented case studies on high altitude slopes in the Chilean Andes (33° S). The model predicts avalanche flow temperature as well as meltwater production, given the thermal initial conditions of the release mass and snowcover entrainment. As the release mass is small, avalanche velocity and runout are primarily controlled by snowcover temperature and moisture content. We demonstrate how the interaction between terrain and entrainment processes influence the production of meltwater and therefore lubrication processes leading to longer runout. This information is useful to avalanche forecasters. An understanding of wet snow avalanche dynamics is important to study how climate change scenarios will influence land usage in mountain regions in the near future.
28
Bozhinskiy, A. N., and L. A. Sukhanov. "Physical modelling of avalanches using an aerosol cloud of powder materials." Annals of Glaciology 26 (1998): 242–46. http://dx.doi.org/10.3189/1998aog26-1-242-246.
Full textAbstract:
The problem of physically modelling snow avalanches with an aerosol cloud is considered. Using the simplest model of avalanche-body motion, the criteria of similarity for transit and deposit zones are written. The transit relations between model and natural scales for dynamic parameters of the avalanche body are established. On the basis of the similarity criteria, an approximate physical model of avalanches with an aerosol cloud is made using a mixture of ferromagnetic sawdust and aluminium dust. The setup allows us to start and stop the model avalanche during any stage of its motion and to model actual avalanches. A series of experiments was completed. It is shown that the basic mechanism of aerosol cloud generation for model avalanches is related to the hydraulic jump of fluid when a stormy flow changes to a calm one. A comparison of parameters for model and “home” avalanches (the vicinity of Elbrus) showed that the ratios of the sizes of dense and aerosol components and deposition zones of those avalanches are close to the geometric scale factor and the ratios of velocities, and durations of processes are close to the square root of this coefficient. The latter corresponds to modelling the process by Froude number.
29
Bozhinskiy, A. N., and L. A. Sukhanov. "Physical modelling of avalanches using an aerosol cloud of powder materials." Annals of Glaciology 26 (1998): 242–46. http://dx.doi.org/10.1017/s0260305500014890.
Full textAbstract:
The problem of physically modelling snow avalanches with an aerosol cloud is considered. Using the simplest model of avalanche-body motion, the criteria of similarity for transit and deposit zones are written. The transit relations between model and natural scales for dynamic parameters of the avalanche body are established. On the basis of the similarity criteria, an approximate physical model of avalanches with an aerosol cloud is made using a mixture of ferromagnetic sawdust and aluminium dust. The setup allows us to start and stop the model avalanche during any stage of its motion and to model actual avalanches. A series of experiments was completed. It is shown that the basic mechanism of aerosol cloud generation for model avalanches is related to the hydraulic jump of fluid when a stormy flow changes to a calm one. A comparison of parameters for model and “home” avalanches (the vicinity of Elbrus) showed that the ratios of the sizes of dense and aerosol components and deposition zones of those avalanches are close to the geometric scale factor and the ratios of velocities, and durations of processes are close to the square root of this coefficient. The latter corresponds to modelling the process by Froude number.
30
Teich, M., J. T. Fischer, T. Feistl, P. Bebi, M. Christen, and A. Grêt-Regamey. "Computational snow avalanche simulation in forested terrain." Natural Hazards and Earth System Sciences 14, no. 8 (August 27, 2014): 2233–48. http://dx.doi.org/10.5194/nhess-14-2233-2014.
Full textAbstract:
Abstract. Two-dimensional avalanche simulation software operating in three-dimensional terrain is widely used for hazard zoning and engineering to predict runout distances and impact pressures of snow avalanche events. Mountain forests are an effective biological protection measure against avalanches; however, the protective capacity of forests to decelerate or even to stop avalanches that start within forested areas or directly above the treeline is seldom considered in this context. In particular, runout distances of small- to medium-scale avalanches are strongly influenced by the structural conditions of forests in the avalanche path. We present an evaluation and operationalization of a novel detrainment function implemented in the avalanche simulation software RAMMS for avalanche simulation in forested terrain. The new approach accounts for the effect of forests in the avalanche path by detraining mass, which leads to a deceleration and runout shortening of avalanches. The relationship is parameterized by the detrainment coefficient K [kg m−1 s−2] accounting for differing forest characteristics. We varied K when simulating 40 well-documented small- to medium-scale avalanches, which were released in and ran through forests of the Swiss Alps. Analyzing and comparing observed and simulated runout distances statistically revealed values for K suitable to simulate the combined influence of four forest characteristics on avalanche runout: forest type, crown closure, vertical structure and surface cover, for example, values for K were higher for dense spruce and mixed spruce-beech forests compared to open larch forests at the upper treeline. Considering forest structural conditions within avalanche simulations will improve current applications for avalanche simulation tools in mountain forest and natural hazard management.
31
Hafner, Elisabeth D., Frank Techel, Silvan Leinss, and Yves Bühler. "Mapping avalanches with satellites – evaluation of performance and completeness." Cryosphere 15, no. 2 (February 24, 2021): 983–1004. http://dx.doi.org/10.5194/tc-15-983-2021.
Full textAbstract:
Abstract. The spatial distribution and size of avalanches are essential parameters for avalanche warning, avalanche documentation, mitigation measure design and hazard zonation. Despite its importance, this information is incomplete today and only available for limited areas and limited time periods. Manual avalanche mapping from satellite imagery has recently been applied to reduce this gap achieving promising results. However, their reliability and completeness have not yet been verified satisfactorily. In our study we attempt a full validation of the completeness of visually detected and mapped avalanches from optical SPOT 6, Sentinel-2 and radar Sentinel-1 imagery. We examine manually mapped avalanches from two avalanche periods in 2018 and 2019 for an area of approximately 180 km2 around Davos, Switzerland, relying on ground- and helicopter-based photographs as ground truth. For the quality assessment, we investigate the probability of detection (POD) and the positive predictive value (PPV). Additionally, we relate our results to conditions which potentially influence avalanche detection in the satellite imagery. We statistically confirm the high potential of SPOT for comprehensive avalanche mapping for selected periods (POD = 0.74, PPV = 0.88) as well as the reliability of Sentinel-1 (POD = 0.27, PPV = 0.87) for which the POD is reduced because mainly larger avalanches are mapped. Furthermore, we found that Sentinel-2 is unsuitable for the mapping of most avalanches due to its spatial resolution (POD = 0.06, PPV = 0.81). Because we could apply the same reference avalanche events for all three satellite mappings, our validation results are robust and comparable. We demonstrate that satellite-based avalanche mapping has the potential to fill the existing avalanche documentation gap over large areas, making alpine regions safer.
32
Turchaninova, A. S., A. V. Lazarev, E. S. Marchenko, Yu G. Seliverstov, S. A. Sokratov, D. A. Petrakov, M. Barandun, R. Kenzhebaev, and T. Saks. "Methods of snow avalanche nourishment assessment (on the example of three Tian Shan glaciers)." Ice and Snow 59, no. 4 (December 1, 2019): 460–74. http://dx.doi.org/10.15356/2076-6734-2019-4-438.
Full textAbstract:
The contribution of snow avalanches to the seasonal snow accumulation on a glacier is among the least studied components of the glacier’s mass balance. The methods for the numerical assessment of avalanche accumulation are still under development, which is related to poor avalanche data availability and difficulties in obtaining such data on most of mountain glaciers. We propose a possible methodology for the numerical assessment of snow avalanche contribution to snow accumulation at mountain glaciers based on DEM and weather data analysis using GIS and numerical modeling of snow avalanches. The developed methodology consists of the following steps: terrain analysis; weather data analysis; snow avalanche volume assessment during an analyzed balance year; numerical simulation of snow avalanches using RAMMS; evaluation of snow avalanches contribution into a glacier accumulation. The proposed methodology was tested on three glaciers located in the Inner Tien Shan: Batysh Sook, № 354 and Karabatkak during the 2015/16 balance year. To evaluate snow avalanche contribution to the seasonal accumulation, we reconstructed avalanche release zones that were most probably active during the 2015/16 balance year and corresponding snow fracture height in each of these zones. The numerical simulations of most probable released snow avalanches during the winter period 2015/16 using avalanche dynamics software RAMMS were performed and compared with the field observations and UAV orthophoto image from July 2016. The outlines of avalanches deposits were realistically reproduced by RAMMS according to the results of field observation. The estimated share of snow avalanche contribution to the accumulation on the research glaciers during the 2015/16 balance year turned out to be: Batysh Sook – 7,4±2,5%; № 354 – 2,2±0,7%; Karabatkak – 10,8±3,6% of the total accumulation. The next step would be to test the proposed methodology based on the data and regional dependences from the Inner Tien Shan in other mountainous regions. This methodology is applicable in the regions where DEMs, regular meteorological observations as well as data on the regional avalanche formation factors are available.
33
Thys, Sien, Maarten Van Daele, Nore Praet, Britta Jensen, Thomas Van Dyck, Peter Haeussler, Elke Vandekerkhove, Veerle Cnudde, and Marc De Batist. "Dropstones in Lacustrine Sediments as a Record of Snow Avalanches—A Validation of the Proxy by Combining Satellite Imagery and Varve Chronology at Kenai Lake (South-Central Alaska)." Quaternary 2, no. 1 (March 1, 2019): 11. http://dx.doi.org/10.3390/quat2010011.
Full textAbstract:
Snow avalanches cause many fatalities every year and damage local economies worldwide. The present-day climate change affects the snowpack and, thus, the properties and frequency of snow avalanches. Reconstructing snow avalanche records can help us understand past variations in avalanche frequency and their relationship to climate change. Previous avalanche records have primarily been reconstructed using dendrochronology. Here, we investigate the potential of lake sediments to record snow avalanches by studying 27 < 30-cm-long sediment cores from Kenai Lake, south-central Alaska. We use X-ray computed tomography (CT) to image post-1964 varves and to identify dropstones. We use two newly identified cryptotephras to update the existing varve chronology. Satellite imagery is used to understand the redistribution of sediments by ice floes over the lake, which helps to explain why some avalanches are not recorded. Finally, we compare the dropstone record with climate data to show that snow avalanche activity is related to high amounts of snowfall in periods of relatively warm or variable temperature conditions. We show, for the first time, a direct link between historical snow avalanches and dropstones preserved in lake sediments. Although the lacustrine varve record does not allow for the development of a complete annual reconstruction of the snow avalanche history in the Kenai Lake valley, our results suggest that it can be used for long-term decadal reconstructions of the snow-avalanche history, ideally in combination with similar records from lakes elsewhere in the region.
34
Molina, Ricard, Elena Muntán, Laia Andreu, Glòria Furdada, Pere Oller, Emilia Gutiérrez, Pere Martínez, and Joan Manue Vilaplana. "Using vegetation to characterize the avalanche of Canal del Roc Roig, Vall de Núria, eastern Pyrenees, Spain." Annals of Glaciology 38 (2004): 159–65. http://dx.doi.org/10.3189/172756404781814807.
Full textAbstract:
AbstractAvalanche hazard maps of high accuracy are difficult to produce. For land-use planning and management purposes, a good knowledge of extreme run-out zones and frequencies of avalanches is required. In the present work, vegetation recognition (especially focused on Pinus uncinata trees) and dendrochronological techniques are used to characterize avalanches that have occurred in historical times, helping to determine both the extent of large or extreme avalanches and their occurrence in time. Vegetation was studied at the Canal del Roc Roig (eastern Pyrenees, Spain) avalanche path. The avalanches descending this path affect the railway that reaches the Vall de Núria resort and the run-up to the opposite slope. During winter 1996, two important avalanches affecting this path were well documented. These are compared with the results of the vegetation study, consisting of an inventory of flora, the recording of vegetation damages along eight transverse profiles at different altitudes on the path and a dendrochronological sampling campaign. The data obtained contributed to a characterization of the predominant snow accumulation in the starting zone, the 1996 avalanches and the range of frequencies of large avalanches. Also, traces of avalanches that increase the path mapped in the avalanche paths map published by the Institut Cartogràfic de Catalunya in 2000 were identified, improving the initial existing information.
35
Buser, Othmar, and Perry Bartelt. "Dispersive pressure and density variations in snow avalanches." Journal of Glaciology 57, no. 205 (2011): 857–60. http://dx.doi.org/10.3189/002214311798043870.
Full textAbstract:
AbstractSnow avalanches possess two types of kinetic energy: the kinetic energy associated with the mean velocity in the downhill direction and the kinetic energy associated with individual particle velocities that vary from the mean. The mean kinetic energy is directional; the kinetic energy associated with the velocity fluctuations is non-directional in the sense that it is connected to random particle movements. However, the rigid, basal boundary directs the random fluctuation energy into the avalanche. Thus, the random energy flux is converted to free mechanical energy which lifts and dilates the avalanche flow mass, changing the flow density and increasing the normal (dispersive) pressure and, as a consequence, changing the flow resistance. In this paper we derive macroscopic relations that link the production of the random kinetic energy to the perpendicular acceleration of the avalanche’s center of mass. We show that a single burst of fluctuation energy will produce pressures that oscillate around the hydrostatic pressure. Because we do not include a damping process, the oscillations of the center of mass remain, even if the production of random kinetic energy stops. We formulate relationships that can be used within the framework of depth-averaged mass and momentum equations that are often used to simulate snow avalanches in realistic terrain.
36
Muntán, E., C. García, P. Oller, G. Martí, A. García, and E. Gutiérrez. "Reconstructing snow avalanches in the Southeastern Pyrenees." Natural Hazards and Earth System Sciences 9, no. 5 (September 28, 2009): 1599–612. http://dx.doi.org/10.5194/nhess-9-1599-2009.
Full textAbstract:
Abstract. A regional study of snow avalanche processes was undertaken in the SE Pyrenees. Dendrogeomorphology was used to date and reconstruct large-scale snow avalanche events that occurred in the last four decades. Dendrochronological analyses yielded the dates of nine winters when avalanches occurred in the recent past in six studied avalanche paths. Some of these avalanches were already known, but others had not been documented. In one case, the existing avalanche path map was improved with the dendrogeomorphological information of a larger past event. As a result of the dendrogeomorphological analyses, evidence for three regional-scale major avalanche years was identified in the SE Pyrenees from 1971 to 2004: 1971–1972, 1995–1996 and 2002–2003. The specific synoptic atmospheric situations and the most likely nivometeorological and snowpack conditions that released these major avalanches were determined using weather data for the seasons of major avalanche releases. In 1971–1972 the snow avalanche episode was characterized by a deep trough crossing the Pyrenees. In 1995–1996 a variety of meteorological situations produced several episodes of major avalanches. In 2002–2003 the more significant of two episodes was attributed to a north advection pumping an arctic air mass over the Pyrenees. The 1995–1996 avalanche season proved to be the most notable in the four past decades in the Pyrenees.
37
Hutter, Kolumban, Yongqi Wang, and Shiva P. Pudasaini. "The Savage–Hutter avalanche model: how far can it be pushed?" Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 363, no. 1832 (June 28, 2005): 1507–28. http://dx.doi.org/10.1098/rsta.2005.1594.
Full textAbstract:
The Savage–Hutter (SH) avalanche model is a depth-averaged dynamical model of a fluid-like continuum implementing the following simplifying assumptions: (i) density preserving, (ii) shallowness of the avalanche piles and small topographic curvatures, (iii) Coulomb-type sliding with bed friction angle δ and (iv) Mohr–Coulomb behaviour in the interior with internal angle of friction ϕ ≥ δ and an ad hoc assumption reducing the number of Mohr's circles in three-dimensional stress states to one. We scrutinize the available literature on information regarding these assumptions and thus delineate the ranges of validity of the proposed model equations. The discussion is limited to relatively large snow avalanches with negligible powder snow component and laboratory sand avalanches starting on steep slopes. The conclusion of the analysis is that the SH model is a valid model for sand avalanches, but its Mohr–Coulomb sliding law may have to be complemented for snow avalanches by a second velocity-dependent contribution. For very small snow avalanches and for laboratory avalanches starting on moderately steep and bumpy slopes it may not be adequate.
38
Bartelt, Perry, Lorenz Meier, and Othmar Buser. "Snow avalanche flow-regime transitions induced by mass and random kinetic energy fluxes." Annals of Glaciology 52, no. 58 (2011): 159–64. http://dx.doi.org/10.3189/172756411797252158.
Full textAbstract:
AbstractWe perform a linear-stability analysis of a system of ordinary differential equations describing the motion of dense flowing avalanches. The depth-averaged equations relate the mean translational velocity of the avalanche to the production of turbulent kinetic energy associated with the random motion of the snow granules. Flow friction is described by an extended Voellmy model, where both the Coulomb and turbulent resistance are related to the random kinetic energy. We identify two snow avalanche flow regimes: (1) an unstable frictional flow regime characterized by low random kinetic energy production and (2) a stable, collisional flow regime at the avalanche front. Flow-regime transitions are governed by the production of random kinetic energy, which is controlled by mass. The unstable regime is characterized by a saddle point which the avalanche encounters at the onset of motion and deposition. Depending on the release mass and/or mass growth, the avalanche head will either fluidize, leading to far-reaching avalanches, or starve and die out. At the tail of the avalanche this saddle point also controls the commencement of deposition and therefore the stopping behaviour of avalanches. We discuss the conditions for flow-regime transitions and the enhanced mobility of snow avalanches.
39
Gruber, Urs, and Stefan Margreth. "Winter 1999: a valuable test of the avalanche-hazard mapping procedure in Switzerland." Annals of Glaciology 32 (2001): 328–32. http://dx.doi.org/10.3189/172756401781819238.
Full textAbstract:
AbstractIn Switzerland three large snowfall periods led to numerous large avalanche events, causing the deaths of 17 people, damage to about 1000 buildings and blockage of many important traffic systems. This situation was a valuable test of the avalanche-hazard mapping procedure developed in Switzerland since the last extreme avalanche winter in 1951. In most cases, the avalanches stopped within the avalanche-hazard zones. However, approximately 40 of about 1200 large avalanche events passed the limits of the existing hazard zones. The primary deficiency was underestimation of the hazard of powder-snow avalanches. The other reason the hazard-zone boundaries were passed was multiple avalanche events in a single track within a short time period. In addition, some fracture depths were larger than those used in avalanche-dynamics calculations. Therefore, the guideline assumptions for defining the fracture depths are questioned. Winter 1999 impressively underlined the danger of avalanches in mountainous regions. It emphasized the importance of avalanche-hazard mapping, showed the existing deficiencies and provided a large amount of field data that will help to improve our knowledge of avalanche dynamics.
40
Steinkogler, W., B. Sovilla, and M. Lehning. "Thermal energy in dry snow avalanches." Cryosphere 9, no. 5 (September 17, 2015): 1819–30. http://dx.doi.org/10.5194/tc-9-1819-2015.
Full textAbstract:
Abstract. Avalanches can exhibit many different flow regimes from powder clouds to slush flows. Flow regimes are largely controlled by the properties of the snow released and entrained along the path. Recent investigations showed the temperature of the moving snow to be one of the most important factors controlling the mobility of the flow. The temperature of an avalanche is determined by the temperature of the released and entrained snow but also increases by frictional processes with time. For three artificially released avalanches, we conducted snow profiles along the avalanche track and in the deposition area, which allowed quantifying the temperature of the eroded snow layers. This data set allowed to calculate the thermal balance, from release to deposition, and to discuss the magnitudes of different sources of thermal energy of the avalanches. For the investigated dry avalanches, the thermal energy increase due to friction was mainly depending on the effective elevation drop of the mass of the avalanche with a warming of approximately 0.3 °C per 100 vertical metres. Contrarily, the temperature change due to entrainment varied for the individual avalanches, from −0.08 to 0.3 °C, and depended on the temperature of the snow along the path and the erosion depth. Infrared radiation thermography (IRT) was used to assess the surface temperature before, during and just after the avalanche with high spatial resolution. This data set allowed to identify the warmest temperatures to be located in the deposits of the dense core. Future research directions, especially for the application of IRT, in the field of thermal investigations in avalanche dynamics are discussed.
41
Margreth, Stefan, and Walter J. Ammann. "Hazard scenarios for avalanche actions on bridges." Annals of Glaciology 38 (2004): 89–96. http://dx.doi.org/10.3189/172756404781814951.
Full textAbstract:
AbstractEngineers require impact scenarios when developing hazard mitigation strategies to protect structures against snow avalanches. Since direct measurements of avalanche impacts on large obstacles are rare, the documentation and post-event analysis of avalanche damages is essential to understand the interaction of avalanches with obstacles. The objective of this paper is to develop hazard scenarios for avalanche actions on bridges, based on a case study of a well-documented avalanche event. The 40 m long pre-stressed road bridge Ri di Rialp in the Swiss Alps collapsed after being struck by a dense-flow avalanche in 1998. The post-event analysis shows that the controlling hazard scenario was an inclined avalanche impact, not a horizontal impact as one would assume given the topographical situation. Using a failure analysis, an impact angle of 40° and a minimal impact pressure of 172 kN m−2 were found. Finally the insights are summarized so that engineers can apply the results when designing a bridge at risk from avalanches.
42
Schaerer, Peter. "The Yield of Avalanche Snow at Rogers Pass, British Columbia, Canada." Journal of Glaciology 34, no. 117 (1988): 188–93. http://dx.doi.org/10.3189/s0022143000032226.
Full textAbstract:
AbstractThe annual mass of snow moved by avalanches was observed at 45 avalanche paths over a period of 19 years by measuring the volume and density of each individual avalanche. Several other methods to estimate the total annual avalanche mass were applied but they were found less efficient owing to inaccuracy and difficulties in timing.For the data set, the yield ratio, i.e. the percentage of snow removed annually by avalanches, had a mean value of 11.2% and a 30 year maximum of 30.9%. The yield ratio varied strongly among avalanche paths and yearly, and could not be explained satisfactorily. The exposure to wind, inclination of the avalanche track, control by artillery, and the winter weather can all have an influence on the value of the parameter.The temporal variability of avalanche yield is erratic but weather patterns frequently associated with high or low yield ratios could be identified. High values are usually associated with large avalanches triggered by major weather events in the late part of the winter.
43
Jóhannesson, Tómas. "Run-up of two avalanches on the deflecting dams at Flateyri, northwestern Iceland." Annals of Glaciology 32 (2001): 350–54. http://dx.doi.org/10.3189/172756401781819382.
Full textAbstract:
AbstractTwo deflecting dams were constructed above the village Flateyri, northwestern Iceland, after the catastrophic avalanche accident on 26 October 1995 when 20 people were killed. Both deflectors have since been hit by moderately large avalanches, in each case with a volume of > 100 000 m3 and an estimated return period of 10–30 years. The avalanches hit the deflectors with deflecting angles of 20–25° and a maximum run-up of 12–13 m. They flowed about 500 m along the deflectors after the initial impact and terminated in the ocean on the respective sides of the reef where the village is situated. Back-calculated impact velocities are of the order of 30 m s–1. In both cases, the impact channelized a part of or The whole of the width of the avalanche into a stream 20–80 m wide, the run-out of which is estimated to have been increased by > 100 m by the deflection of the avalanche by the dam. Although the avalanches are much smaller than the design avalanches of the deflecting dams, they have provided avalanche professionals and the public in Iceland with much-welcomed direct evidence of the effectiveness of the defence structures at Flateyri against moderately sized events. They also provide unique direct observations for further scientific investigations of the deflection of avalanches by man-made deflecting dams.
44
Fedorov, I. S., A. V. Fedorov, and V. E. Asming. "Registration of avalanches in the Khibiny Mountains by the geophysical methods." Vestnik MGTU 24, no. 1 (March 31, 2021): 69–79. http://dx.doi.org/10.21443/1560-9278-2021-24-1-69-79.
Full textAbstract:
In the winter months of 2018-2020 the Kola Branch of the Unified Geophysical Service RAS conducted experiments on the joint registration of avalanches in the Khibiny mountain range using seismic and infrasonic sensors during work on the forced descent of the snow mass. The aim of the experiments is to assess the possibility of avalanche detection using the geophysical methods. The lack of representative statistics on the frequency and regularity of avalanches is the reason for the relevance of developing methods of their remote registration. The difficulty of registering avalanches is due to their occurrence often in hard-to-reach areas and in poor visibility conditions. To record signals generated by avalanches, different configurations of infrasound panels consisting of three spatially separated sensors (MPA 201 or Hyperion IFS-4000 microbarographs) and a portable seismic station Guralp CMG-6TD were used. As a result of the experiments, infrasound recordings were obtained at different distances from the avalanche source. The infrasound group recordings collected from the experiments were processed using an automatic detector implementing amplitude and cross-correlation signal detection methods. The spectral composition of the recordings and their characteristic appearance were analyzed. Avalanche-induced signals are characterized by long duration and changes in azimuth to the source. The dominant frequencies of the signal lie in the region of 1-10 Hz. Conclusions are made about the insufficient sensitivity of the seismic method when the seismometer is located at a distance of the first kilometers from the avalanche source, as well as the high applicability of the infrasound method for recording the facts of avalanches. The results obtained will make it possible to develop a methodology for automatic detection of signals generated by avalanches using the data of infrasound registration. This is the necessary basis for building a system for continuous monitoring of avalanche activity.
45
Rice, Robert, Rand Decker, Newel Jensen, Ralph Patterson, and Stanford Singer. "Rural Intelligent Transportation System for Snow Avalanche Detection and Warning." Transportation Research Record: Journal of the Transportation Research Board 1700, no. 1 (January 2000): 17–23. http://dx.doi.org/10.3141/1700-04.
Full textAbstract:
The growth of winter travel on alpine roads in the western United States, a result of the demand for reliable winter access, has increased the hazard to motorists and highway maintenance personnel from snow avalanches. Configurations are presented for systems that can detect and provide, in real time, warnings to motorists and highway maintainers of roadway avalanches. These warnings include on-site traffic control signing, in-vehicle audio alarms for winter maintenance vehicles, and notifying maintenance facilities or centralized agency dispatchers. These avalanche detection and warning systems can detect an existing avalanche and use the avalanche’s remaining time of descent to initiate on-site alarms. Alternatively, real-time knowledge and notification of the onset of avalanching may be used to proactively manage the evolving hazard over an affected length or corridor of highway. These corridors can be several tens of kilometers in length and may be very remote, low-volume rural highways. As a consequence, these detection and warning systems must be cost-effective alternatives to existing avalanche hazard reduction technology. Results and experiences from the winters of 1997–1998 and 1998–1999 are presented, along with recommendations and criteria for future deployment of these automated natural hazard reduction systems for rural transportation corridors.
46
Leinss, Silvan, Raphael Wicki, Sämi Holenstein, Simone Baffelli, and Yves Bühler. "Snow avalanche detection and mapping in multitemporal and multiorbital radar images from TerraSAR-X and Sentinel-1." Natural Hazards and Earth System Sciences 20, no. 6 (June 19, 2020): 1783–803. http://dx.doi.org/10.5194/nhess-20-1783-2020.
Full textAbstract:
Abstract. Snow avalanches can endanger people and infrastructure, especially in densely populated mountainous regions. In Switzerland, the public is informed by an avalanche bulletin issued twice a day during winter which is based on weather information and snow and avalanche reports from a network of observers. During bad weather, however, information about avalanches that have occurred can be scarce or even be missing completely. To assess the potential of weather-independent radar satellites, we compared manual and automatic change detection avalanche mapping results from high-resolution TerraSAR-X (TSX) stripmap images and medium-resolution Sentinel-1 (S1) interferometric wide-swath images for a study site in central Switzerland. The TSX results were also compared to available mapping results from high-resolution SPOT-6 optical satellite images. We found that avalanche outlines from TSX and S1 agree well with each other. Cutoff thresholds of mapped avalanche areas were found with 500 m2 for TSX and 2000 m2 for S1. S1 provides a much higher spatial and temporal coverage and allows for mapping of the entire Alps at least every 6 d with freely available acquisitions. With costly SPOT-6 images the Alps can even be covered in a single day at meter resolution, at least for clear-sky conditions. For the SPOT-6 and TSX mapping results, we found a fair agreement, but the temporal information from radar change detection allows for a better separation of overlapping avalanches. Still, the total mapped avalanche area differed by at least a factor of 3 because with radar mainly the avalanche deposition zone was detected, whereas the release zone was very visible already in SPOT-6 data. With automatic avalanche mapping we detected around 70 % of manually mapped new avalanches, at least when the number of old avalanches is low. To further improve the radar mapping capabilities, we combined S1 images from multiple orbits and polarizations and obtained a notable enhancement of resolution and speckle reduction such that the obtained mapping results are almost comparable to the single-orbit TSX change detection results. In a multiorbital S1 mosaic covering all of Switzerland, we manually counted 7361 new avalanches which occurred during an extreme avalanche period around 4 January 2018.
47
Nishimura, K., H. Narita, N. Maeno, and K. Kawada. "The Internal Structure of Powder-Snow Avalanches." Annals of Glaciology 13 (1989): 207–10. http://dx.doi.org/10.1017/s0260305500007904.
Full textAbstract:
The internal structure of powder-snow avalanches was investigated at Kurobe Canyon in the Shiai-dani area of Japan in 1988. Internal velocity was derived for avalanches of this kind by frequency analysis of impact-force data, and was found to undergo a remarkable change with time. The shear of the avalanche flow was estimated to range from 1 to 7 s−1. The front region of the avalanche wind was observed to precede the front of the avalanche by a distance of 17.3 m. The maximum wind velocity was comparable with the internal velocity of the front region of the avalanche.
48
Nishimura, K., H. Narita, N. Maeno, and K. Kawada. "The Internal Structure of Powder-Snow Avalanches." Annals of Glaciology 13 (1989): 207–10. http://dx.doi.org/10.3189/s0260305500007904.
Full textAbstract:
The internal structure of powder-snow avalanches was investigated at Kurobe Canyon in the Shiai-dani area of Japan in 1988. Internal velocity was derived for avalanches of this kind by frequency analysis of impact-force data, and was found to undergo a remarkable change with time. The shear of the avalanche flow was estimated to range from 1 to 7 s−1. The front region of the avalanche wind was observed to precede the front of the avalanche by a distance of 17.3 m. The maximum wind velocity was comparable with the internal velocity of the front region of the avalanche.
49
Takeuchi, Yukari, and Hiroyuki Hirashima. "Snowpack estimations in the starting zone of large-scale snow avalanches in the Makunosawa valley, Myoko, Japan." Annals of Glaciology 54, no. 62 (2013): 19–24. http://dx.doi.org/10.3189/2013aog62a155.
Full textAbstract:
AbstractThe Makunosawa valley, Myoko, Japan, experiences frequent avalanches and is therefore ideally suited to study how meteorological elements influence avalanche activity. Since 2000, five large-scale snow avalanches with running distances >2000 m have been observed and some characteristics of these avalanches have been obtained. However, the characteristics of the snowpack in the starting zones could not be observed because they are too difficult to approach and no snow-pit observations have been carried out. We simulated the variations in the snowpack in the starting zone using the numerical snowpack model SNOWPACK with local meteorological data. The results indicate a layer of faceted crystals with low shear strength followed by rapid loading from snowfall was the cause of three avalanches in February. Conversely, no layer of faceted crystals was shown by the model before a January avalanche and we assume the sliding surface of the avalanche to be precipitation particles. The only wet-snow avalanche is attributed to a decrease in shear strength due to infiltration of meltwater and an increase in liquid water content in the boundary of two layers of different grain sizes.
50
Feistl, Thomas, Peter Bebi, Michaela Teich, Yves Bühler, Marc Christen, Kurosch Thuro, and Perry Bartelt. "Observations and modeling of the braking effect of forests on small and medium avalanches." Journal of Glaciology 60, no. 219 (2014): 124–38. http://dx.doi.org/10.3189/2014jog13j055.
Full textAbstract:
AbstractA long-standing problem in avalanche science is to understand how forests stop avalanches. In this paper we quantify the effect of forests on small and medium avalanches, crucial for road and skirun safety. We performed field studies on seven avalanches where trees affected the runout. We gathered information concerning the release zone location and dimension, deposition patterns and heights, runout distance and forest structure. In these studies the trees were not destroyed, but acted as rigid obstacles. Wedge-like depositions formed behind (1) individual tree stems, (2) dense tree groups and (3) young trees with low-lying branches. Using the observations as a guide, we developed a one-parameter function to extract momentum corresponding to the stopped mass from the avalanche. The function was implemented in a depth-averaged avalanche dynamics model and used to predict the observed runout distances and mean deposition heights for the seven case studies. The approach differs from existing forest interaction models, which modify avalanche friction to account for tree breakage and debris entrainment. Our results underscore the importance of forests in mitigating the danger from small-to-medium avalanches.