Channel activity of past debris flows at the Bruchji torrent (Aletsch region, Valais)

The purpose of this study was to reconstruct spatio-temporal patterns of debris-flow events at the Bruchji torrent. Therefore, a detailed geomorphic map was elaborated in a first step serving as a basis for the sampling of heavily affected trees on the debris-flow cone.

Tree-ring analysis allowed reconstruction of 40 event years between 1867 and 1996. Through the precise localisation of the affected trees on the map spatial patterns for the events could be determined. In total 11 formerly active debris-flow channels were identified and their activity assessed. Past debris-flow events at the Bruchji torrent showed five different patterns of spatial activity. Until the 1930s, especially the western part of the cone was affected before the event of 1935 influenced for the first time also the eastern sector.

Project applicants : Swiss Federal Office for Water and Geology (FOWG); Forest and Landscape Authority of the Canton of Valais; Road and River Engineering Authority of the Canton of Valais; Naters community


Collaboration : Department of Physical Geography, University of Frankfurt /M. (Germany)

Contact : Markus Stoffel

Publications :

Bollschweiler M., Stoffel M., Ehmisch M., Monbaron M., 2007: Reconstructing spatio-temporal patterns of debris-flow activity using dendrogeomorphological methods. Geomorphology. 87, 337-351. [PDF]

Bollschweiler, M., Stoffel, M., Ehmisch, M. (2006): Channel activity of debris flows on forested cones a case study using dendrogeomorphology . Geophysical Research Abstract 8, 06463. [PDF]

Ehmisch, M. & Bollschweiler, M. (2005): Temporal and spatial variations of debris-flow activity on a forested cone a dendrogeomorphological approach. Eurodendro 2005, International Conference of Dendrochronology. 28. September 2. Oktober 2005. Viterbo.

Bollschweiler M. & Ehmisch M. (2003): Past debris flow activity from tree-ring analysis at the Bruchji torrent, Valais , Switzerland. In: TRACE - Tree Rings in Archaeology, Climatology and Ecology, Vol. 2: Proceedings of the DENDROSYMPOSIUM 2003, May 1st 3rd 2003, Utrecht. Schriften des Forschungszentrums Jülich. Reihe Umwelt/Environment: 31-35