28 Mar 2022
28 Mar 2022
Status: this preprint is currently under review for the journal ESurf.

Rockfall trajectory reconstruction: A flexible method utilizing video footage and high-resolution terrain models

François Noël1,2, Michel Jaboyedoff1, Andrin Caviezel3, Clément Hibert4, Franck Bourrier5, and Jean-Philippe Malet4,6 François Noël et al.
  • 1Risk Analysis Group, Institute of Earth Sciences, University of Lausanne, CH-1015 Lausanne, Switzerland
  • 2Geohazard and Earth Observation, Geological Survey of Norway – NGU, NO-7040 Trondheim, Norway
  • 3WSL Institute for Snow and Avalanche Research SLF, CH-7260 Davos, Switzerland
  • 4ITES/Institut Terre et Environnement de Strasbourg, CNRS UMR7063 CNRS – Université de Strasbourg, 5 rue Descartes, F-67084 Strasbourg, France
  • 5Université Grenoble Alpes, INRAE, ETNA, 38000 Grenoble, France
  • 6École et Observatoire des Sciences de la Terre, CNRS UAR 830 CNRS – Université de Strasbourg, 5 rue Descartes, F67084 Strasbourg, France

Abstract. Many rockfall simulation software provide great flexibility to the user at the expense of a hardly achievable parameter unification. With sensitive site-dependent parameters that are hardly generalizable from the literature and case studies, the user must properly calibrate simulations for the desired site by performing back calculation analyses. Thus, rockfall trajectory reconstruction methods are needed. For that purpose, a computer-assisted videogrammetric 3D trajectory reconstruction method (CAVR) built on earlier approaches is proposed. Rockfall impacts are visually identified and timed from video footage, and are manually transposed on detailed high-resolution 3D terrain models that act as the spatial reference. This shift of reference removes the dependency on steady and precisely positioned cameras, ensuring that the CAVR method can be used for reconstructing trajectories from witnessed previous records with nonoptimal video footage. For validation, the method is applied to reconstruct some trajectories from a rockfall experiment performed by the WSL Institute for Snow and Avalanche Research SLF. The results are compared to previous ones from the SLF and share many similarities. Indeed, the translational energies, bounce heights, rotational energies and impact positions against a flexible barrier compare well with those from the SLF. Interestingly, only dissipative impact processes are observed with the CAVR method, contrary to the previous results from the SLF. The comparison shows that the presented cost-effective and flexible CAVR method can reproduce proper 3D rockfall trajectories from experiments or real rockfall events.

François Noël 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 esurf-2022-16', Anonymous Referee #1, 10 May 2022
  • RC2: 'Comments on esurf-2022-16', Anonymous Referee #2, 28 Jun 2022

François Noël et al.

François Noël et al.


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Short summary
Rockfall simulations are often performed to make sure infrastructures are safe. For that purpose, rockfall trajectory data is needed to calibrate the simulation models. In this paper, an affordable, flexible, and efficient trajectory reconstruction method is proposed. The method is tested by reconstructing trajectories from a full-scale rockfall experiment involving 2670 kg rocks and a flexible barrier. The results highlight improvements in precision and accuracy of the proposed method.