04 Feb 2022
04 Feb 2022
Status: this preprint is currently under review for the journal NHESS.

Delimiting rockfall runout zones using reach probability values simulated with a Monte-Carlo based 3D trajectory model

Luuk Dorren1,11, Frédéric Berger2,11, Franck Bourrier2, Nicolas Eckert2,3, Charalampos Saroglou4, Massimiliano Schwarz1,11, Markus Stoffel5,6,7, Daniel Trappmann8, Hans-Heini Utelli9, and Christine Moos1,10 Luuk Dorren et al.
  • 1Bern University of Applied Sciences BFH-HAFL, Länggasse 85, CH-3052 Zollikofen, Switzerland
  • 2INRAE, Grenoble, France
  • 3Univ. Grenoble Alpes, Grenoble, France
  • 4School of Civ. Eng., Nat. Techn. Univ. Athens, Greece
  • 5Climatic Change Impacts and Risks in the Anthropocene (C-CIA), Institute for Environmental Sciences, University of Geneva, Geneva, Switzerland
  •, Department of Earth Sciences, University of Geneva, Geneva, Switzerland
  • 7Department of F.A. Forel for Environmental and Aquatic Sciences, University of Geneva, Geneva, Switzerland
  • 8Bayerische Staatsforsten, Marquartstein, Germany
  • 9Impuls AG, Thun, Switzerland
  • 10CIRM - Univ. of Lausanne, Sion, Switzerland
  • 11Int. ecorisQ Association, P.O. Box 2348, 1211 Geneva 2, Switzerland

Abstract. At present, a quantitative basis for delimiting realistic rockfall runout zones on the basis of trajectory simulation data is generally missing. The objective of this study is to come up with standardized reach probability threshold values (RPTV) to separate "realistic" from "unrealistic" simulated rockfall runouts. We therefore compared reach probability values (Preach) simulated with Rockyfor3D for 458 mapped, fresh rockfall blocks (silent witnesses SW) on 18 different sites with a volume >= 0.05 m3 and estimated occurrence frequencies up to 300 years. We analysed which block, slope and forest characteristics influenced Preach of the SW based on a linear mixed effects model. The results indicate that the limit of a realistic runout zone lies in the range where simulated Preach values are between > 1 % and approximately 3 %. We conclude that RPTV can be defined to values lying in the range from 1.2 % to 2.5 % depending on the defined block volume and the encountered cumulative basal area in a forested transit zone. Where possible, the defined RPTV should be compared and validated by field recordings of SW.

Luuk Dorren et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2022-32', Anonymous Referee #1, 15 Feb 2022
    • AC1: 'Reply on RC1', Luuk Dorren, 08 Mar 2022
  • RC2: 'Comment on nhess-2022-32', Anonymous Referee #2, 09 Mar 2022
    • AC2: 'Reply on RC2', Luuk Dorren, 05 Apr 2022

Luuk Dorren et al.

Luuk Dorren et al.


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Short summary
In the daily practice of rockfall hazard analysis, trajectory simulations are used to delimit runout zones. To do so, the expert needs to separate "realistic" from "unrealistic" simulated groups of trajectories. This is often done on the basis of reach probability values. This paper provides a basis for choosing a reach probability threshold value for delimiting the rockfall runout zone, based on recordings and simulations of recent rockfall events at 18 active rockfall sites in Europe.