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| Titel |
The Illgraben sediment cascade, 1963-2009 |
| VerfasserIn |
Georgie Bennett, Henri Eisenbeiss, Peter Molnar, Brian McArdell, Fritz Schlunegger, Paolo Burlando |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250053235
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| Zusammenfassung |
| Several studies have identified the importance of landslides and remobilization of stored
sediment in debris flow generation. Long-term sediment budgets are required to understand
the relative contribution of these processes to sediment transfer in debris flow dominated
catchments and to identify source zones for debris flows. In this study we used digital
photogrammetry to quantify erosion, storage and remobilization of sediment within the active
rock face and main channel of the Illgraben debris flow catchment, southwest Switzerland, in
the decades following a large bedrock landslide in 1961 that choked the channel with
3–5Ã106 m3 sediment.
We produced Digital Elevation Models (DEMs) for 1963, 1986, 1992, 1998, 2007, 2008
and 2009. To ensure a common reference plane all DEMs were registered to the 2005
Swiss-Topo LIDAR DEM in the ETH-developed LS3D. Error bounds, calculated based on
the standard deviations of selected stable points used in registration, are between 0.6 and
2.7 m. We quantified sediment transfer in two main zones: the active rock face
to the south of the channel head, and the channel between its head and the upper
fan.
Over the observation period the active rock face eroded at a rate of 0.4 m-
yr-1,
feeding sediment into a cascade of sediment storage zones along the debris flow
channel. Decadal cycles of sediment depletion and recharge occurred along the
channel but with an overall depletion of 20% of the sediment deposited in the 1961
rockfall, at rate of 0.1 m-
yr-1. Channel residence time of sediment, calculated as the
ratio of stored sediment to debris flow flux, was ~90 years. In total 8Ã106 m3
sediment was evacuated, which is in good agreement with the part estimated and part
measured debris flow flux over the period, 90% of which was from the rock face zone. |
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