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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 16, issue 7 | Copyright
Nat. Hazards Earth Syst. Sci., 16, 1657-1672, 2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 20 Jul 2016

Research article | 20 Jul 2016

Influence of expertise on rockfall hazard assessment using empirical methods

Adeline Delonca, Thierry Verdel, and Yann Gunzburger Adeline Delonca et al.
  • UMR 7359 GeoRessources, Université de Lorraine, CNRS, CREGU École des Mines, Campus Artem, CS2434, 54042 Nancy Cedex, France

Abstract. To date, many rockfall hazard assessment methods still consider qualitative observations within their analysis. Based on this statement, knowledge and expertise are supposed to be major parameters of rockfall assessment. To test this hypothesis, an experiment was carried out in order to evaluate the influence of knowledge and expertise on rockfall hazard assessment. Three populations were selected, having different levels of expertise: (1) students in geosciences, (2) researchers in geosciences and (3) confirmed experts. These three populations evaluated the rockfall hazard level on the same site, considering two different methods: the Laboratoire des Ponts et Chaussées (LPC) method and a method partly based on the "slope mass rating" (SMR) method. To complement the analysis, the completion of an "a priori" assessment of the rockfall hazard was requested of each population, without using any method. The LPC method is the most widely used method in France for official hazard mapping. It combines two main indicators: the predisposition to instability and the expected magnitude. Reversely, the SMR method was used as an ad hoc quantitative method to investigate the effect of quantification within a method. These procedures were applied on a test site divided into three different sectors.

A statistical treatment of the results (descriptive statistical analysis, chi-square independent test and ANOVA) shows that there is a significant influence of the method used on the rockfall hazard assessment, whatever the sector. However, there is a non-significant influence of the level of expertise of the population the sectors 2 and 3. On sector 1, there is a significant influence of the level of expertise, explained by the importance of the temporal probability assessment in the rockfall hazard assessment process. The SMR-based method seems highly sensitive to the "site activity" indicator and exhibits an important dispersion in its results. However, the results are more similar with the LPC qualitative method, even in the case of sector 1.

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Short summary
Rockfall hazard zoning analyses can be based on qualitative observations. For this reason, expertise is of great importance in determining the hazard. To test this hypothesis, an experiment is proposed to evaluate the importance of subjective assessment: three populations with different level of expertise assessed the level of rockfall hazard on three sites using a qualitative and a quantitative method. A statistical analysis shows that there is a non-significant influence of the level of expertise.
Rockfall hazard zoning analyses can be based on qualitative observations. For this reason,...