Tree-ring reconstruction of past overbank sedimentation events out of the current debris-flow channel at Illgraben (Leuk-Susten)

The Illgraben near Leuk-Susten is the most active debris-flow torrent of Switzerland with several events per year. In the departure zone of the Illgraben, enormous amounts of heavily disintegrated quartzite, limestone and gypsum are easily mobilized during precipitation events. In addition, mass movements regularly delivered debris into or close to the channel, allowing the formation of one of the largest debris-flow cones of the European Alps over the Holocene. In the framework of the RUFINE project, detailed dendrogeomorphological analyses will be performed on the Illgraben cone. During a first field campaign in summer 2006, more than 1004 increment cores and cross-sections from 493 Scots pine trees (Pinus sylvestris L.) have been sampled in the neighborhood of the current debris-flow channel. Preliminary results on past overbank sedimentation events out of the main channel as well as on past activity in abandoned flow paths can be expected by fall 2007. In summer 2007, additional fieldwork and dendrogeomorphological investigations are planned in order to analyze past debris-flow activity along the banks of the current channel as well as in the distal parts of the cone.


Contractors: Swiss Federal Office for the Environment (FOEN), Cantonal Department for Traffic, Construction and Environment (Canton of Valais)

Contractors: Swiss Federal Research Institute for Forest, Snow and Landscape (WSL), Birmensdorf

Project duration: August 2006 – September 2008

Contact: Markus Stoffel


Stoffel, M., Bollschweiler, M., Leutwiler, A., Aeby, P. (2008): Large debris-flow events and overbank sedimentation in the Illgraben torrent (Valais Alps, Switzerland). Open Geology Journal 2: 18–29. [PDF]

Aeby, P., Leutwiler, A. 2007. Reconstruction of debris-flow activity on the Illgraben cone (Valais Alps, Switzerland). Geophysical Research Abstract 9, 05972. [PDF]