Field experiments and numerical modeling of mass entrainment in snow avalanches

Sovilla, Betty; Burlando, Paolo; Bartelt, Perry

doi:10.1029/2005jf000391

Cited by 192 publications

(261 citation statements)

References 21 publications

(46 reference statements)

Supporting

Mentioning

242

Contrasting

Unclassified

Order By: Relevance

“…The radars are usually used to analyze the snow entrainment by looking at the evolution of the bottom layer of the flow . Slow basal erosion and a more spontaneous and rapid entrainment of a whole layer of snow can be differentiated [Sovilla et al, 2006]. The FMCW radars are useful in detecting small-scale flow structures that cannot be distinguished in the GEODAR signal since they resolve through the flow rather than across the flow.…”

Section: Upward Looking Fmcw Radarmentioning

confidence: 99%

“…In addition, there may also be enhanced drag due to plowing effects. Certainly, entrainment is extremely important and can have a large effect on flow dynamics in general [Sovilla et al, 2006]. Later, flowing avalanches are possibly entraining older deposits instead of fresh snow.…”

Section: Effective Frictionmentioning

confidence: 99%

“…The overtaking of the leading edge shows that a simplistic model of an avalanche moving with a slowly varying velocity does not agree with the data as the front velocity is discontinuous. Sovilla et al [2006] observed with buried and upward looking FMCW radar that avalanches can entrain large amount of snow well behind the leading edge by a process which they called step entrainment. However, the GEODAR data in combination with the laser scan data suggest that this entrainment mechanism is not a process where the mass is entrained along an abrupt erosion front but rather due to the instantaneous failure of snow slabs.…”

Section: Velocity Of Surgesmentioning

confidence: 99%

“…The surge not only showed up as an increase in flow height change but also entrained instantaneously around 1 m from the old snow cover. Sovilla et al [2006] characterized such instantaneous erosion as step entrainment, which is driven by the front of a surge. But the laser scan data ( Figure 5) clearly show that the area #4 has a sharp boundary and suggests that a secondary release, the failure of a snow slab, happened.…”

Section: Major Surgesmentioning

confidence: 99%

“…They can detect layers in the snowpack as well as observe the flowing snow as it passes over them. They give a detailed but qualitative picture of entrainment, deposition, flow height, and flow structure [Salm and Gubler, 1985;Sovilla et al, 2006].…”

Section: Upward Looking Fmcw Radarmentioning

confidence: 99%

See 4 more Smart Citations

The dynamics of surges in the 3 February 2015 avalanches in Vallée de la Sionne

Köhler¹,

McElwaine

Sovilla³

et al. 2016

JGR Earth Surface

View full text Add to dashboard Cite

Five avalanches were artificially released at the Vallée de la Sionne test site in the west of Switzerland on 3 February 2015 and recorded by the GEOphysical flow dynamics using pulsed Doppler radAR Mark 3 radar system. The radar beam penetrates the dilute powder cloud and measures reflections from the underlying denser avalanche features allowing the tracking of the flow at 111 Hz with 0.75 m downslope resolution. The data show that the avalanches contain many internal surges. The large or “major” surges originate from the secondary release of slabs. These slabs can each contain more mass than the initial release, and thus can greatly affect the flow dynamics, by unevenly distributing the mass. The small or “minor” surges appear to be a roll wave‐like instability, and these can greatly influence the front dynamics as they can repeatedly overtake the leading edge. We analyzed the friction acting on the fronts of minor surges using a Voellmy‐like, simple one‐dimensional model with frictional resistance and velocity‐squared drag. This model fits the data of the overall velocity, but it cannot capture the dynamics and especially the slowing of the minor surges, which requires dramatically varying effective friction. Our findings suggest that current avalanche models based on Voellmy‐like friction laws do not accurately describe the physics of the intermittent frontal region of large mixed avalanches. We suggest that these data can only be explained by changes in the snow surface, such as the entrainment of the upper snow layers and the smoothing by earlier flow fronts.

show abstract

Section: Upward Looking Fmcw Radarmentioning

confidence: 99%

Section: Effective Frictionmentioning

confidence: 99%

Section: Velocity Of Surgesmentioning

confidence: 99%

Section: Major Surgesmentioning

confidence: 99%

Section: Upward Looking Fmcw Radarmentioning

confidence: 99%

See 3 more Smart Citations

The dynamics of surges in the 3 February 2015 avalanches in Vallée de la Sionne

Köhler¹,

McElwaine

Sovilla³

et al. 2016

JGR Earth Surface

View full text Add to dashboard Cite

show abstract

Fundamental changes of granular flow dynamics, deposition, and erosion processes at high slope angles: Insights from laboratory experiments

Farin

Mangeney

Roche

2014

J. Geophys. Res. Earth Surf.

108

139

View full text Add to dashboard Cite

International audienceEntrainment of underlying debris by geophysical flows can significantly increase the flow deposit extent. To study this phenomenon, analog laboratory experiments have been conducted on granular column collapse over an inclined channel with and without an erodible bed made of similar granular material. Results show that for slope angles below a critical value θc, between 10° and 16°, the run out distance rf depends only on the initial column height h0 and is unaffected by the presence of an erodible bed. On steeper slopes, the flow dynamics change fundamentally, with a slow propagation phase developing after flow front deceleration, significantly extending the flow duration. This phase has characteristics similar to those of steady uniform flows. Its duration increases with increasing slope angle, column volume, column inclination with respect to the slope and channel width, decreasing column aspect ratio (height over length), and in the presence of an erodible bed. It is independent, however, of the maximum front velocity. The increase in the duration of the slow propagation phase has a crucial effect on flow dynamics and deposition. Over a rigid bed, the development of this phase leads to run out distances rf that depend on both the initial column height h0 and length r0. Over an erodible bed, as the duration of the slow propagation phase increases, the duration of bed excavation increases, leading to a greater increase in the run out distance compared with that over a rigid bed (up to 50%). This effect is even more pronounced as bed compaction decreases

show abstract

Entrainment of bed material by Earth‐surface mass flows: Review and reformulation of depth‐integrated theory

Iverson

Ouyang

2015

Reviews of Geophysics

235

135

View full text Add to dashboard Cite

Earth-surface mass flows such as debris flows, rock avalanches, and dam-break floods can grow greatly in size and destructive potential by entraining bed material they encounter. Increasing use of depth-integrated mass and momentum conservation equations to model these erosive flows motivates a review of the underlying theory. Our review indicates that many existing models apply depth-integrated conservation principles incorrectly, leading to spurious inferences about the role of mass and momentum exchanges at flow-bed boundaries. Model discrepancies can be rectified by analyzing conservation of mass and momentum in a two-layer system consisting of a moving upper layer and static lower layer. Our analysis shows that erosion or deposition rates at the interface between layers must, in general, satisfy three jump conditions. These conditions impose constraints on valid erosion formulas, and they help determine the correct forms of depth-integrated conservation equations. Two of the three jump conditions are closely analogous to Rankine-Hugoniot conditions that describe the behavior of shocks in compressible gasses, and the third jump condition describes shear traction discontinuities that necessarily exist across eroding boundaries. Grain-fluid mixtures commonly behave as compressible materials as they undergo entrainment, because changes in bulk density occur as the mixtures mobilize and merge with an overriding flow. If no bulk density change occurs, then only the shear traction jump condition applies. Even for this special case, however, accurate formulation of depth-integrated momentum equations requires a clear distinction between boundary shear tractions that exist in the presence or absence of bed erosion.

show abstract

Field experiments and numerical modeling of mass entrainment in snow avalanches

Cited by 192 publications

References 21 publications

The dynamics of surges in the 3 February 2015 avalanches in Vallée de la Sionne

The dynamics of surges in the 3 February 2015 avalanches in Vallée de la Sionne

Fundamental changes of granular flow dynamics, deposition, and erosion processes at high slope angles: Insights from laboratory experiments

Entrainment of bed material by Earth‐surface mass flows: Review and reformulation of depth‐integrated theory

Contact Info

Product

Resources

About