Assessing the protective effect of mountain forests against rockfall using a 3D simulation model

Abstract

We used one of the few rockfall models explicitly taking trees into account and compared the results obtained with the 3D simulation model RockyFor with empirical data on tree impacts at three mountain forests in Switzerland. Even though we used model input data with different resolutions at the study sites, RockyFor accurately predicted the spatial distribution of trajectory frequencies at all sites. In contrast, RockyFor underestimated mean impact heights observed on trees at the two sites where high-and medium-resolution input data were available and overestimated them at the site where input data with the lowest resolution data were used. By comparing the results of the simulation scenarios ''current forest cover'' and ''non-forested slope'', we assessed the protective effect of the current stands at all three sites. The number of rocks reaching the bottom parts of the study sites would, on average, almost triple if the ''current forest cover'' were absent.We conclude that RockyFor is able to predict the spatial distribution of rockfall trajectories on forested slopes accurately, based on input data with a resolution of at least 5 m  5 m. With the increasing availability of high-resolution data, it provides a useful tool for assessing the protective effect of mountain forests against rockfall.

Tree-ring based reconstruction of the seasonal timing, major events and origin of rockfall on a case-study slope in the Swiss Alps

“…Furthermore, there are a large number of studies on rockfall modeling (Guzzetti et al, 2002;Dorren et al, 2006;Stoffel et al, 2006b) or on long-term accretion rates of rockfall (Luckman and Fiske, 1995;McCarroll et al, 1998). In addition, research has focused on possible triggers of rockfall such as tectonic folding (Coe and Harp, 2007), freeze-thaw cycles (Gardner, 1983;Matsuoka and Sakai, 1999;Matsuoka, 2006), changes in the rock-moisture level (Sass, 2005), the thawing of permafrost (Gruber et al, 2004), the rising of mean annual temperatures (Davies et al, 2001) or the occurrence of earthquakes (Harp and Wilson, 1995;Marzorati et al, 2002).…”

Energy dissipation of rockfalls by coppice structures

“…(Chauvin et al, 1994 ;Wasser and Frehner, 1996;Frehner et al, 2005;Stoffel et al, 2006) However, the development of technical specifications is required for coppice structures.…”

Evaluation of a 3-D rockfall module within a forest patch model

“…Furthermore, reported rebound heights usually do not exceed 2 m to 4 m while simulated rebound heights are much higher (e.g. Stoffel et al, 2006; see also Fig. 3).…”

“…Reasons are that rockfall is one of the most common natural hazards in mountainous landscapes, and that the protective effect of many European mountain forests may decrease in the future due to abundant old-growth phases with a lack of regeneration (e.g., Ott et al, 1997;BFW, 2004). To study the development of the protective effect as well as the influence of forest management, reliable simulation tools are required which are able to take into account the spatial pattern of rockfall processes on slopes as well as the effect of forest vegetation composition and structure on run-out distances and kinetic energies of falling rocks (Stoffel et al, 2006;Dorren et al, 2005). Due to the long time horizons of regeneration processes in mountain forests, models must be able to cope with time scales of several decades.…”