On the importance of snowpack stability, the frequency distribution of snowpack stability, and avalanche size in assessing  the avalanche danger level

Techel, Frank; Müller, Karsten; Schweizer, Jürg

doi:https://doi.org/10.5194/tc-14-3503-2020

Articles | Volume 14, issue 10

https://doi.org/10.5194/tc-14-3503-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/tc-14-3503-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 14, issue 10

Research article

|

22 Oct 2020

Research article |

| 22 Oct 2020

On the importance of snowpack stability, the frequency distribution of snowpack stability, and avalanche size in assessing the avalanche danger level

Frank Techel, Karsten Müller, and Jürg Schweizer

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Final revised paper (published on 22 Oct 2020)
Preprint (discussion started on 21 Feb 2020)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'Review of "On the importance of snowpack stability, its frequency distribution, and avalanche size in assessing the avalanche danger level: a data-driven approach"', Simon Horton, 22 Mar 2020
- AC2: 'Reply to review by Simon Horton', Frank Techel, 09 May 2020
RC2: 'Review of:', Karl W. Birkeland, 24 Apr 2020
- AC1: 'Reply to review by Karl Birkeland', Frank Techel, 09 May 2020

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Publish subject to revisions (further review by editor and referees) (19 May 2020) by Guillaume Chambon

AR by Frank Techel on behalf of the Authors (18 Jun 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (07 Jul 2020) by Guillaume Chambon

RR by Simon Horton (09 Jul 2020)

Suggestions for revision or reasons for rejection

General comments

The authors have substantially improved the manuscript by addressing my main comment about the presentation of the results. The new structure addresses the objective of the paper in a more logical and intuitive way by directly addressing each of the key factors contributing to avalanche danger and then combining them into a practical look-up table. They have also addressed my other comments appropriately. My main remaining concern is the results section on bootstrap sampling is still slightly confusing with figures that don’t necessarily support the main arguments in a clear way (see comment bellow). I also have some other minor comments on the revised manuscript below.

Specific comments
• Sect. 4.1.2: I appreciate how this section and Fig. 4 present the frequency of very poor stability in a clear way. I would consider modifying the section title and adding an introductory sentence to clarify that these frequencies come from sampling (e.g. “sampled” frequency of very poor stability). The example of what these frequencies mean in terms of 25 RB tests is a nice way to link these classes to practical field applications.
• proportion vs. frequency: Please check the usage of these terms which are mixed throughout the paper. When discussing the key factor “frequency of triggering spots” it would make sense to use the term “frequency” (e.g. axis labels in Fig. 4, Fig. 7a, etc.). There is also a mix of reporting frequencies as a decimals and percentages (e.g. 0.04 and 4%). Using standard formatting and labelling for your derived frequencies would be helpful.
• Fig. 4: Caption should be more detailed and explain how these proportions come from a sampling method. This will help explain how this figure differs from the data presented in Fig. 3. Also, this figure could be cited at the start of the paragraph about correlations between frequency classes and danger level (p11 l3).
• Table 2: Please explain what the interval means in the caption (i.e. proportion of very poor stability).
• Fig. 6: The percentages below the danger matrix are only explained in the text, but not in the figure or caption.
• Fig. 6/7: This new figure layout links the lookup table and raw data in a much clearer way. Thanks.
• Sect 4.6: The section on bootstrap sampling is still rather complex and difficult to understand. I find lines 1-5 on page 18 and its links to Fig. 8 particularly challenging to understand. First do the results you describe in text refer to Fig. 8c as written or Fig. 8b? I’m not sure where I can see these values in Fig. 8. How does describing the percentage of samples with very poor and good stability relate to the typical distributions for each danger level? Are we supposed to compare these percentages with Fig. 2 or Fig. 9 to see that 11% of very poor results is within a typical range for 3-Considerable danger? Also, why is a threshold between few and several of 8% used here when elsewhere the threshold is 4%? Fig. 9 is also rather complex and difficult to interpret. Is the purpose to compare bootstrapping with n = 10 and n = 25 or is it to compare sampled and observed distributions? Based on the text in Sect 4.6.1 it seems to be about agreement between bootstrapped samples and field observations. If so, is it still necessary to have a 6-panel figure? While these extra results were appropriate in the Appendix their purpose in the main body of the results is less clear. Also, what is the significance of sentence in the caption about the distributions between Mod and Con danger for good stability n = 10? If this is important to validating the bootstrapping method it should be explained in the results. Overall I think this section and Fig 8 and 9 could still be presented in a clearer way to justify the bootstrapping method.

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RR by Karl W. Birkeland (30 Jul 2020)

ED: Publish subject to minor revisions (review by editor) (10 Aug 2020) by Guillaume Chambon

AR by Frank Techel on behalf of the Authors (23 Aug 2020) Author's response Manuscript

ED: Reconsider after major revisions (further review by editor and referees) (01 Sep 2020) by Guillaume Chambon

ED: Publish as is (10 Sep 2020) by Guillaume Chambon

AR by Frank Techel on behalf of the Authors (10 Sep 2020) Author's response Manuscript

Short summary

Exploring a large data set of snow stability tests and avalanche observations, we quantitatively describe the three key elements that characterize avalanche danger: snowpack stability, the frequency distribution of snowpack stability, and avalanche size. The findings will aid in refining the definitions of the avalanche danger scale and in fostering its consistent usage.