Differentiation of debris-flow and snow avalanche impacts in coniferous woods on the Birchbach cone (Lötschental, Valais)
Trees on the cone of the Birchbach torrent (Lötschental, Valais) are disturbed by debris flows as well as by snow avalanches originating from three different couloirs. Dendrogeomorphological methods allowed spatio-temporal reconstructions of debris flows and avalanches for the last 200 years. The accurate analysis of the samples allowed assignation of the growth disturbances to one of the two processes. Traumatic rows of resin ducts in the beginning of a new tree ring were assigned to an avalanche event taking place during the dormancy of trees between October and May. In contrast, traumatic rows of resin ducts occurring in the latewood of a tree ring were assigned to a debris-flow event. Nine of the 30 event years in the tree rings were assigned to avalanche events whereas 19 events are the result of debris-flow activity.
Collaboration : Department of Geography, University of Bonn (Germany)
Contact : Markus Stoffel
Stoffel. M., Bollschweiler, M., Hassler, G. R., Monbaron, M. (2008): Reconstitution de la dynamique des avalanches dans le Nanztal et le Lötschental (Valais) par méthodes dendrogéomorphologiques. Bulletin de la Murithienne 125: 89- 97 [PDF]
Stoffel, M., Bollschweiler, M., Hassler, G. R. (2006): Differentiating past events on a cone influenced by debris-flow and snow avalanche activity – a dendrogeomorphological approach. Earth Surface Processes and Landforms 31 (11), 1424-1437. [PDF]