11 May 2023
 | 11 May 2023
Status: this preprint is open for discussion.

Avalanche size estimation and avalanche outline determination by experts: reliability and implications for practice

Elisabeth D. Hafner, Frank Techel, Rodrigo Caye Daudt, Jan Dirk Wegner, Konrad Schindler, and Yves Bühler

Abstract. Consistent estimates of avalanche size are crucial for communicating among avalanche practitioners, but also between avalanche forecasters and the public, as for instance in public avalanche forecasts. Moreover, applications such as risk management and numerical avalanche simulations rely on accurately mapped outlines of past avalanche events. Since there is no widely applicable and objective way to measure avalanche size nor to determine the outlines of an avalanche, humans estimate these. Therefore, knowing about the reliability of avalanche size estimates and avalanche outlines is essential as errors will impact applications relying on this kind of data. Conducting three user studies, we investigate the reliability in avalanche size estimates and avalanche outlines either mapped from oblique photographs or from remotely-sensed imagery. We compare size estimates for 10 avalanches made by 170 avalanche professionals working in Europe or North America, the mappings of six avalanches from oblique photographs from 10 participants, and the mappings of avalanches visible on 2.9 km2 of remotely-sensed imagery in four different spatial resolutions from five participants. We observed an average agreement in the avalanche size estimated by the majority of respondents of 66 %, while agreement with the avalanche size considered «correct» was 74 %. Moreover, European avalanche practitioners rated avalanches significantly larger for eight out of 10 avalanches, compared to North Americans. For the outlines mapped from oblique photographs, we noted a mean overlapping proportion of 52 % for any two avalanche mappings and 60 % compared to a reference mapping. The outlines mapped from remotely-sensed imagery had a mean overlapping proportion of 46 % (image resolution 2 m) to 68 % (25 cm) between any two mappings, and 64 % (2 m) to 80 % (25 cm) when compared to the reference. Assuming that participants are equally competent in the estimation of avalanche size or the determination of avalanche outlines, we calculated a score describing the factor required to obtain the proportion of agreements between any two size estimates or overlap in avalanche areas. This factor was 0.72 for avalanche size estimates in our data set. It can be regarded as the certainty related to a size estimate by an individual, and thus provides an indication of the reliability of a label. The presented findings demonstrate that the reliability of size estimates and of mapped avalanche outlines is limited. As these data are often used as reference data or even ground truth to validate further applications, the discovered limitations and uncertainties may influence results and should be to be taken into account.

Elisabeth D. Hafner et al.

Status: open (until 22 Jun 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-586', Ivan Moner, 29 May 2023 reply
  • RC2: 'Comment on egusphere-2023-586', Brian Lazar, 07 Jun 2023 reply

Elisabeth D. Hafner et al.

Elisabeth D. Hafner et al.


Total article views: 168 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
129 31 8 168 14 2 1
  • HTML: 129
  • PDF: 31
  • XML: 8
  • Total: 168
  • Supplement: 14
  • BibTeX: 2
  • EndNote: 1
Views and downloads (calculated since 11 May 2023)
Cumulative views and downloads (calculated since 11 May 2023)

Viewed (geographical distribution)

Total article views: 174 (including HTML, PDF, and XML) Thereof 174 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
Latest update: 08 Jun 2023
Short summary
Oftentimes when objective measurements are not possible, human estimates are used instead. In our study, we investigate the reproducibility of human judgement for size estimates, the mappings of avalanches from oblique photographs and remotely-sensed imagery. The variability that we found in those estimates is worth considering as it may influence results and should be kept in mind for several applications.