Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
Nat. Hazards Earth Syst. Sci., 8, 203-211, 2008
https://doi.org/10.5194/nhess-8-203-2008
© Author(s) 2008. This work is licensed under
the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.
 
11 Mar 2008
Tree-ring based reconstruction of the seasonal timing, major events and origin of rockfall on a case-study slope in the Swiss Alps
D. M. Schneuwly and M. Stoffel Laboratory of Dendrogeomorphology, Department of Geosciences, University of Fribourg, Chemin du Musée 4, 1700 Fribourg, Switzerland
Abstract. Tree-ring analysis has been used to reconstruct 22 years of rockfall behavior on an active rockfall slope near Saas Balen (Swiss Alps). We analyzed 32 severely injured trees (L. decidua, P. abies and P. cembra) and investigated cross-sections of 154 wounds.

The intra-annual position of callus tissue and of tangential rows of traumatic resin ducts was determined in order to reconstruct the seasonality of past rockfall events. Results indicate strong intra- and inter-annual variations of rockfall activity, with a peak (76%) observed in the dormant season (early October – end of May). Within the growth season, rockfall regularly occurs between the end of May and mid July (21.4%), whereas events later in the season appear to be quite rare (2.6%). Findings suggest that rockfall activity at the study site is driven by annual thawing processes and the circulation of melt water in preexisting fissures. Data also indicate that 43% of all rockfall events occurred in 1995, when two major precipitation events are recorded in nearby meteorological stations. Finally, data on impact angles are in very good agreement with the geomorphic situation in the field.


Citation: Schneuwly, D. M. and Stoffel, M.: Tree-ring based reconstruction of the seasonal timing, major events and origin of rockfall on a case-study slope in the Swiss Alps, Nat. Hazards Earth Syst. Sci., 8, 203-211, https://doi.org/10.5194/nhess-8-203-2008, 2008.
Publications Copernicus
Download
Share