Université de Fribourg

Spatial and temporal occurrence of past debris flows in the Valais Alps : Results from tree-ring analysis

Bollschweiler, Michelle ; Monbaron, Michel (Dir.)

Thèse de doctorat : Université de Fribourg, 2007 ; Nr. 1572.

Debris flows are common mass-movement processes in most mountainous regions of the world, where their unpredictable and sudden occurrence represents a major threat to transportation corridors and settlements. Increased anthropogenic activity in regions exposed to debris-flow risk renders a detailed hazard assessment inevitable. However, archival data on past events remains scarce and, most of the...

Université de Fribourg

Reconstructing spatio-temporal patterns of debris-flow activity using dendrogeomorphological methods

Bollschweiler, Michelle ; Stoffel, Markus ; Ehmisch, Melanie ; Monbaron, Michel

In: Geomorphology, 2007, vol. 87, no. 4, p. 337-351

Debris flows are a major threat in many parts of the Alps, where they repeatedly cause severe damage to infrastructure and transportation corridors or even loss of life. Nonetheless, the spatial behavior of past debris-flow activity and the analysis of areas affected during particular events have been widely neglected in reconstructions so far. It was therefore the purpose of this study to...

Université de Fribourg

Dynamics in debris-flow activity on a forested cone — A case study using different dendroecological approaches

Bollschweiler, Michelle ; Stoffel, Markus ; Schneuwly, Dominique M.

In: Catena, 2008, vol. 72, no. 1, p. 67-78

Dendrogeomorphological analyses of trees affected by debris flows have regularly been used to date past events. However, this method has always been limited to forested cones where trees registered the impact of previous events. The minimum age dating of trees growing in the debris deposits can, in contrast, provide information on the latest possible moment of past activity. In this paper, we...

Université de Fribourg

Differentiating past events on a cone influenced by debris-flow and snow avalanche activity - a dendrogeomorphological approach

Stoffel, Markus ; Bollschweiler, Michelle ; Hassler, Gion-Reto

In: Earth Surface Processes and Landforms, 2006, vol. 31, no. 11, p. 1424 - 1437

Dendrogeomorphology was used to investigate past events on a cone affected by both debris flows and snow avalanches. We report on results of 520 cores from 251 injured Larix decidua Mill. and Picea abies (L.) Karst. trees sampled on the Birchbach cone (Swiss Alps). Detailed analysis of tree-ring sequences allowed dating of 561 growth disturbances in individual trees for a 252 yr...