Exploring debris-flow history and process dynamics using an integrative approach on a dolomitic cone in western Austria

Authors

  • Emily Procter,

    1. Laboratory of Dendrogeomorphology, Institute of Geological Sciences, University of Berne, Berne, Switzerland
    Search for more papers by this author
  • Markus Stoffel,

    Corresponding author
    1. Laboratory of Dendrogeomorphology, Institute of Geological Sciences, University of Berne, Berne, Switzerland
    • Climatic Change and Climate Impacts, Environmental Sciences, University of Geneva, Carouge-Geneva, Switzerland
    Search for more papers by this author
  • Michelle Schneuwly-Bollschweiler,

    1. Laboratory of Dendrogeomorphology, Institute of Geological Sciences, University of Berne, Berne, Switzerland
    2. Climatic Change and Climate Impacts, Environmental Sciences, University of Geneva, Carouge-Geneva, Switzerland
    Search for more papers by this author
  • Mathias Neumann

    1. Laboratory of Dendrogeomorphology, Institute of Geological Sciences, University of Berne, Berne, Switzerland
    2. Institute of Mountain Risk Engineering, University of Natural Resources and Applied Life Sciences, Vienna, Austria
    Search for more papers by this author

Markus Stoffel, Laboratory of Dendrogeomorphology, Institute of Geological Sciences, University of Berne, Baltzerstrasse 1 + 3, CH-3012 Berne, Switzerland. E-mail: markus.stoffel@dendrolab.ch

ABSTRACT

The evolution of a debris-flow cone depends on a multitude of factors in the hydrogeomorphic system. Investigations of debris-flow history and cone dynamics in highly active catchments therefore require an integrative approach with a temporal and spatial resolution appropriate for the goals of the study. We present the use of an orthophoto time series to augment standard dendrogeomorphic techniques to describe the spatio-temporal dynamics of debris flows on a highly active cone in the western Austrian Alps. Analysis of seven orthophotos since 1951 revealed a migration of active deposition areas with a resulting severe loss of forest cover (> 80%) and a mean tree loss per year of 10·4 (range 1·3–16·6 trees per year). Analysis of 193 Pinus mugo ssp. uncinata trees allowed the identification of 161 growth disturbances corresponding to 16 debris flows since 1839 and an average decadal frequency of 0·9 events. As a result of the severe loss of forest cover, we speculate that < 20% of the more recent events were actually captured in the tree-ring record, giving a decadal return interval of ~7·5 events for a period of 60 years. Based on three annual field observations, it is evident that this catchment (the Bärenrüfe) produces very frequent (< 1 yr), small (in the order of a few 10 to 100 m3) debris flows with minor material relocation. The specific challenges of tree-ring analysis in this tree species and in highly active environments are explicitly addressed in the discussion and underline the necessity of employing complementary methods of analysis in an integrative manner. Copyright © 2012 John Wiley & Sons, Ltd.

Ancillary