the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 27 Aug 2024
The source, quantity, and spatial distribution of interfacial water during glide-snow avalanche release: experimental evidence from field monitoring
Abstract. Glide-snow avalanches release at the soil-snow interface due to a loss friction which is suspected to be linked to interfacial water. To date, the formation and distribution of the interfacial water are not well understood, and glide-snow avalanches are considered unpredictable. We investigated the source, quantity, and spatial distribution of interfacial water before and during avalanche release through spatio-temporal field monitoring. The measurement setup consists of a sensor grid covering a slope with frequent glide-snow avalanche activity. The 24 grid sensors measured the soil temperature and liquid water content (LWC) throughout the seasons 2021/22 to 2023/24. Snow/interfacial temperature and LWC were monitored locally with a vertical sensor profile ranging from the soil into the snow. Seven glide-snow avalanches released on the sensor grid and their investigation showed: (i) interfacial water originated from geothermal heat, rain, and meltwater percolation, (ii) the quantity of snow LWC was lower for glide-snow avalanches that released in early winter than in spring, (iii) soil temperatures below the release area were higher than in the remaining slope if interfacial water originated from geothermal heat (iv) if interfacial water originated from rain/melt we observed (locally) higher soil LWC below the release area and (v) for four avalanches the spatial variability of soil LWC across the slope reached a local minimum at the time of avalanche release. In the future, with continued monitoring, the spatio-temporal investigation of the soil will help to quantify the drivers for glide-snow avalanche release at the slope scale. This will contribute to improved glide-snow avalanche forecasting and mitigation.
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RC1: 'Comment on egusphere-2024-2485', Anonymous Referee #1, 02 Oct 2024
The paper investigates the source, quantity, and spatial distribution of interfacial water before and during glide - snow avalanche release. As the liquid water at the snow soil interface is a key predisposing factor for glide avalanche release, this paper significantly contribute to the comprehension of this natural phenomenon. I really appreciate the efforts to observe and measure the snow and soil properties jointly, since together they represent a highly dynamic and connected porous medium.
The paper is well written, minor issues are listed below:
Line 12: maybe better “for the majority of the snow avalanches considered in the study” rather than four avalanches
Line 14: please specify what kind of soil properties have to be considered
Line 17: change infrastructure into infrastructures
Line 29: I would add layer after liquid water
Line 51: I would specify at what soil depth grid sensors measured the soil temperature and LWC across the slope
Caption in Figure 2: Please explain the meaning of the different colours in the graph
Line 75: How the slope is protected? Because of the lower slope angle? Because of some active protections?
Line 76: May you provide some more information about the soil? What is the soil classification? Moreover I think that not only the texture but also the soil organic matter content could influence the water retention.
Line 308: I think that in Ceaglio et al. 2017 the potential contribution of groundwater in the study area could have been higher than in your study site, saturating the soil with a potential higher movement of water from soil to the lowermost layer of the snowpack.
Line 337: I fully agree that soil soil inhomogeneities and preferential flow patterns could explain the spatial variability of the local temperature/soil LWC. I would add also the plant cover inhomogeneities which could change the surface roughness.
Line 389: correct avalanches
Citation: https://doi.org/10.5194/egusphere-2024-2485-RC1 -
RC2: 'Comment on egusphere-2024-2485', Anonymous Referee #2, 12 Dec 2024
General comments: The manuscript describes the influence of soil temperature, soil LWC and snow LWC on the formation of glide snow avalanches. The authors found that for interface events the snow LWC was lower (∼3 %) than for surface events (∼7 %). For most events, the soil temperatures in the release area were higher 8 days preceding an avalanche, and this was associated with geothermal heat and higher soil LWC during those 8 days. The spatial variability of soil LWC in many cases showed a local minimum at the time of release.
Although the investigations are based on only seven events the manuscript is an important contribution to better understand the influencing factors of glide snow avalanches.
However, there are major deficiencies with respect to diagrams and figures; in some diagrams the various graphs cannot really be distinguished (since the colors are very similar); some other figures are too small to discern specific details – for more information see below.
Specific points:
Line 19: it should be read as `Fankhauser´ [not `Frankhauser´]; the authors should correct the name also in the References.
Table 2: in the second line of Table 2 it should read as ` (24,2,2) ´ [not ` (20, 2,2) ´].
Figure 4:
1) it is difficult to distinguish between the various colors in Figure 4b; please use other signatures.
2) It would be useful to give a short note on the criteria of interface, mixed and surface events; certainly, there is a description in the paper, but it would be nice to have that information also in the caption of the diagram.
Line 187: does the wording `below the release area´ mean `in the release area´? (with reference to the following figures).
Figure 6:
1) it is difficult to distinguish between the various colors in Figure 6.
2) the authors should explain the horizontal shades (blue, grey, orange…) in the first row (soil LWC) and third row (Tsoil).
3) several lines are not visible (e.g. in c4 it is not possible to discern the line for Snow LWC in 10cm – it is visible only if one zooms into the figure).
Line 210: the authors write: `…we observed above-average soil LWC below the release area´
1) there is no specification on the average of soil LWC.
2) does the wording `below the release area´ mean `in the release area´?
Figure 7: it is difficult to distinguish between blue and black dots.
Line 217: the authors write: `…up to the release area caused above-average soil LWC´. There is no specification on the average of soil LWC.
Line 218: the authors write: `… no indication of meltwater percolation (Figure 6f1, f3, f6) …´. Where is diagram f6?
Line 239 - 240: the authors write: `The soil LWC, matric potential and interface sensors all showed an increase in available water at the interface and in the soil (Figure 6d1, d2, d4, e1, e2, e4) ´. The described increase cannot be seen in Figure 6e4.
Line 285 – 287: The sentence `However, the overall soil LWC…. of the surface events on 16 Mar 2022, 25 Dec 2023, and 27 Jan 2024 (Figure 10c, d, f) ´ is not clear. The authors should improve that sentence.
Line 292: the authors write: ` …minimum soil variability…´. I think the authors mean ` …minimum soil LWC variability…´
Figure 10: the authors write in the caption: `Temporal evolution of the spatial variability before avalanche release…´. I think the authors mean `Temporal evolution of the spatial soil LWC variability before avalanche release …´
Line 330: The term `warmer air temperature´ is not reasonable; it should mean `higher air temperature´
Line 334 - 335: the authors write: `Generally, we observed… below the release areas compared to the rest of the slope´ Does the wording `below the release area´ mean `in the release area´?
Line 357: I think there must be a mistake when the authors indicate an avalanche release on 2. Dec 2024. (the paper was submitted before that date).
Citation: https://doi.org/10.5194/egusphere-2024-2485-RC2
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