Wirkung des Waldes im Transit- und Ablagerungsgebiet von Hangmuren

Dorren, Luuk; Moos, Christine; Hollard, Niels; Noyer, Estelle; Schaller, Christoph; Günter, Mark; May, Alexander Dominik Ezuma; Schwarz, Massimiliano; Brühwiler, Valentin Jonas; Erbach, Alexandra; Vuaridel, Marceline; von Wattenwyl, Kim Fabian; Thormann, Jean-Jacques (2023). Wirkung des Waldes im Transit- und Ablagerungsgebiet von Hangmuren Schweizerische Zeitschrift für Forstwesen, 174(S1), s21-s29. Schweizerischer Forstverein 10.3188/szf.2023.s0021

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In Switzerland, spontaneous shallow landslides and hillslope debris flows cause high infrastructure damage, closures of important infrastructure, evacuations and sometimes fatalities every year. At the latest since the introduction of the cycle of integral management of natural hazard risks, the protection forest is the most important biological measure against shallow landslides and hillslope debris flows. The focus is usually on the effect of the protection forest in the landslide fracture area. However, there is often evidence in the field that the forest also has a protective effect in the transit and deposition areas of hillslope debris flows, not only in the fracture area. Nevertheless, the protective effect of forests in the transit and deposition areas of hillslope debris flows has not yet been systematically investigated. Therefore, the aim of this study was to measure the relevant forest structure parameters that determine the protective effect. In addition, we quantified this effect by means of a risk assessment in two case studies. With the help of analyses of historical hillslope debris flow events in combination with terrain surveys in the forest, it could be shown that the braking effect of the forest is mainly influenced by the number of trunks. As the density of the forest increases, the length of the runout distance decreases. In addition, it could be shown that significantly more material can be deposited behind thicker trees. This suggests that a well-structured stand with a high number of trunks, but also occasional large diameters, offers ideal protection against hillslope debris flows in the transit and deposition area. The results of the laboratory tests indicate that the braking effect of different forest structures (dense, open, with gaps) is always given compared to a situation without forest, and this at lower (16%) and higher (20%) water contents. Runout sections of historical hillslope debris flow events with and without forest in the transit section could be reproduced with DEM-based simulations with rigid cylinders with BHD > 20 cm and allowed a calculation and monetisation of the protective effect of forest in the transit section of hillslope debris flows. This showed that the risk-reducing effect of forest in the transit area of a hillslope debris flow can amount to CHF 6,500/year for a motorway similar to the Gotthard section.

Item Type:	Journal Article (Original Article)
Division/Institute:	School of Agricultural, Forest and Food Sciences HAFL School of Agricultural, Forest and Food Sciences HAFL > Multifunctional Forest Management > Mountain Forests, Natural Hazards and GIS
Name:	Dorren, Luuk0000-0001-9344-9461; Moos, Christine; Hollard, Niels; Noyer, Estelle; Schaller, Christoph0000-0002-8013-2892; Günter, Mark; May, Alexander Dominik Ezuma0000-0003-0753-5801; Schwarz, Massimiliano0000-0003-4652-8102; Brühwiler, Valentin Jonas; Erbach, Alexandra; Vuaridel, Marceline; von Wattenwyl, Kim Fabian and Thormann, Jean-Jacques
Subjects:	Q Science > QE Geology S Agriculture > SD Forestry
ISSN:	0036-7818
Publisher:	Schweizerischer Forstverein
Language:	German
Submitter:	Luuk Dorren
Date Deposited:	18 Oct 2023 10:35
Last Modified:	11 Dec 2023 15:28
Publisher DOI:	10.3188/szf.2023.s0021
Uncontrolled Keywords:	hillslope debris flow, protection forest, barrier effect, natural hazard risk, simulation
ARBOR DOI:	10.24451/arbor.20164
URI:	https://arbor.bfh.ch/id/eprint/20164