Simulation of Snow-Avalanche Flow in Run-Out Zones

Norem, Harald; Irgens, Fridtjov; Schieldrop, Bonsak

doi:10.3189/s026030550000793x

Cited by 30 publications

(28 citation statements)

References 11 publications

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“…Differences of colonisation and of lichen size observed between deposits could be linked to the slope angle and length of the rock wall above each deposit. It was shown that these variables control snow avalanche run-out distances (Voellmy, 1955;Norem et al, 1989;Jomelli, 1997). These variables could explain the fact that for a certain relative position on a profile, the size of the five largest lichens is not equal between two deposits situated in the same valley.…”

Section: Discussionmentioning

confidence: 99%

Effects of the Little Ice Age on avalanche boulder tongues in the French Alps (Massif des Ecrins)

Jomelli

Pech

2004

Earth Surf Processes Landf

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Lichens of the subspecies Rhizocarpon geographicum s.l were measured on 25 avalanche boulder tongues in the Massif des Ecrins to elucidate the Little Ice Age history of avalanche activity. Results show: (1) an increase of lichen size from the median to the distal zone of deposits, and a decrease from the edges to the centre; (2) three types of lichen settlement. From the uppermost to the median zone, lichens are absent, because avalanche activity is very active. Down-slope, lichens occur in two different zones: the median zone is colonized by 5-20 mm size lichens on sides of blocks protected from the abrasional action of avalanches, while in the distal zone lichen diameters are largest (>30 mm) and occur on all sides of the blocks.The spatial distribution of the lichens and their size according to elevation make it possible to distinguish different phases during which avalanche activity has increased. At high elevation, the avalanche activity was at a maximum before AD 1650 and between AD 1730 and 1830. During these two periods avalanches had sufficient magnitude to reach the basal zone of the deposits. At low elevation since AD 1650 the magnitude and frequency of avalanches have declined.

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Section: Discussionmentioning

confidence: 99%

Effects of the Little Ice Age on avalanche boulder tongues in the French Alps (Massif des Ecrins)

Jomelli

Pech

2004

Earth Surf Processes Landf

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“…Although velocities can be estimated in three-dimensional terrain with the help of numerical models, there exists no accurate relationship to find the avalanche impact pressures, given the avalanche velocity and density. This is in large part due to the fact that existing hydrodynamic formulas for the impact pressure do not take into account the wide range of avalanche flow regimes, which can vary between wet, viscous flows to dry, granular flows [Savage and Hutter, 1991;Norem et al, 1987Norem et al, , 1989. In this paper we address this problem by studying measurements of avalanche impact pressures as a function of the avalanche flow regime.…”

Section: Introductionmentioning

confidence: 99%

Impact pressures and flow regimes in dense snow avalanches observed at the Vallée de la Sionne test site

Sovilla¹,

Schaer²,

Kern³

et al. 2008

J. Geophys. Res.

112

127

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[1] A fundamental problem in avalanche engineering is to determine the impact pressures exerted on structures. This task is complicated because snow avalanches flow in a variety of regimes, primarily depending on snow temperature and moisture content. In this paper we address this problem by analyzing measured impact pressures, flow velocities, and flow depths of five Vallée de la Sionne avalanches. The measurements are made on a 20 m high tubular pylon instrumented with high-frequency pressure transducers and optoelectronic velocity sensors. In the observed avalanches, we find both subcritical and supercritical flow regimes. Typical Froude numbers were smaller than 6. The subcritical regime (Fr < 1) is characterized by a flow plug riding above a highly sheared basal layer. The measured pressures are large and velocity-independent in contradiction to calculation procedures. Pressure fluctuations increase with flow depth, indicating a kinematic stick-slip phenomena which is largest at the basal layer. Supercritical flow regimes (1 < Fr < 6) are characterized by a sheared flow all over the avalanche depth. In this regime the impact pressure is velocity-dependent. We derive relationships governing impact pressure as a function of the Froude number, and therefore flow regime, encompassing all the observed avalanches.Citation: Sovilla, B., M. Schaer, M. Kern, and P. Bartelt (2008), Impact pressures and flow regimes in dense snow avalanches observed at the Vallée de la Sionne test site,

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“…H. NOREM a proposé plusieurs formulations pour décrire les écoulements de neige et il aboutit à une loi de comportement complexe de la forme [NOREM, 1986[NOREM, , 1989[NOREM, , 1992: où la masse de l'avalanche a été assimilée à une masse ponctuelle M située au centre de gravité cie l'écoulement supposé en bloc, où N désigne la composante normale cie la réaction et où F j désigne la force résultante de frottement; la force de frottement écrite sous la forme:…”

Section: Le Modèle De Reiner-rivlin (7)unclassified

Modélisation des avalanches denses Approches théorique et numérique

Ancey¹

1994

La Houille Blanche

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Simulation of Snow-Avalanche Flow in Run-Out Zones

Cited by 30 publications

References 11 publications

Effects of the Little Ice Age on avalanche boulder tongues in the French Alps (Massif des Ecrins)

Effects of the Little Ice Age on avalanche boulder tongues in the French Alps (Massif des Ecrins)

Impact pressures and flow regimes in dense snow avalanches observed at the Vallée de la Sionne test site

Modélisation des avalanches denses Approches théorique et numérique

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