Abstract
The Illgraben catchment is one of the most active torrents in the European Alps, with between 2 and 7 debris flows or similar debris floods occurring every year since the start of systematic observations from 2000 to the present. The ultimate cause of the debris-flow activity is the presence of a variety of rock types, which have been substantially deformed and fractured due to tectonic processes. The change in the orientation of the major Alpine Simplon fault line resulted in the development of many additional faults, which is the cause of the highly fractured bedrock. Sediment delivery to the torrent-channel system is dominated by landslides, the deposits of which are temporarily stored within the channel. Subsequent mobilization of sediment, mainly by intense rainfall, results in the formation of debris flows and debris floods, which entrain the sediment within the torrent system and potentially endanger the community.
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Acknowledgments
The research at the Illgraben has been greatly facilitated by the innovative ideas and competent assistance from WSL technical staff, including B. Fritschi, S. Boss, and C. Graf. Many of the ideas presented herein resulted from interesting discussions with collaborators. We regret if any such ideas have not been properly acknowledged in the citations herein. We are also grateful for the helpful comments and constructive editing by E. Reynard.
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McArdell, B.W., Sartori, M. (2021). The Illgraben Torrent System. In: Reynard, E. (eds) Landscapes and Landforms of Switzerland. World Geomorphological Landscapes. Springer, Cham. https://doi.org/10.1007/978-3-030-43203-4_25
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