Preprints
https://doi.org/10.5194/esurf-2022-21
https://doi.org/10.5194/esurf-2022-21
 
02 Jun 2022
02 Jun 2022
Status: a revised version of this preprint was accepted for the journal ESurf and is expected to appear here in due course.

Modelling deadwood for rockfall mitigation assessments in windthrow areas

Adrian Ringenbach1,2,4, Peter Bebi1,2, Perry Bartelt1,2, Andreas Rigling3,4, Marc Christen1,2, Yves Bühler1,2, Andreas Stoffel1,2, and Andrin Caviezel1,2 Adrian Ringenbach et al.
  • 1Climate Change, Extremes, and Natural Hazards in Alpine Regions Research Center CERC, 7260 Davos Dorf, Switzerland
  • 2WSL Institute for Snow and Avalanche Research SLF, 7260 Davos Dorf, Switzerland
  • 3Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111 8903 Birmensdorf, Switzerland
  • 4Department of Environmental Systems Science, Institute of Terrestrial Ecosystems, ETH Zürich, Zurich, Switzerland

Abstract. How deadwood mitigates rockfall hazard in mountain forests is a key scientific question to understand the influence of climate induced disturbances on the protective capacity of mountain forests. To address this question both experimental quantification combined with numerical process modelling are needed. Modelling provides detailed insights into the rock-deadwood interaction and therefore can be used to develop effective forest management strategies. Here, we introduce an automatic deadwood generator (ADG) to assess the impact of fresh woody storm debris on the protective capacity of a forest stand against rockfall. The creation of deadwood scenarios allows us to directly quantify their mitigation potential. To demonstrate the functionality of the proposed ADG method, we compare genuine deadwood log patterns, their effective height, and ruggedness at two natural windthrow areas at Lake Klöntal, Switzerland, to their generated counterparts. We perform rockfall simulations for the time a) before, b) directly after and c) 10 years after the storm. The results are compared to scenario d) a complete clearing of the thrown wood, in other words a no forest scenario. We showcase an integration of deadwood in rockfall simulations with realistic, deadwood configurations alongside with a DBH- and rot fungi dependent maximal deadwood breaking energy. Our results confirm the mitigation effect of deadwood significantly reducing the jump heights and velocities for 400 kg rocks. Our modelling results suggest that even after a decade, deadwood has a stronger protective effect against rockfall compared to standing trees. An ADG can contribute to the decision making in forest and deadwood management after disturbances.

Adrian Ringenbach et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2022-21', Anonymous Referee #1, 13 Jul 2022
  • RC2: 'Comment on esurf-2022-21', Anonymous Referee #2, 22 Aug 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2022-21', Anonymous Referee #1, 13 Jul 2022
  • RC2: 'Comment on esurf-2022-21', Anonymous Referee #2, 22 Aug 2022

Adrian Ringenbach et al.

Adrian Ringenbach et al.

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Short summary
The presented automatic deadwood generator (ADG) allows us to consider deadwood in rockfall simulations in unprecedented detail. Besides three-dimensional fresh deadwood cones, we include old woody debris in rockfall simulations based on a higher compaction rate and lower energy absorption thresholds. Simulations including different deadwood states indicate that a ten-year-old deadwood pile has a higher protective capacity than a pre-storm forest stand.