EGU21-15399
https://doi.org/10.5194/egusphere-egu21-15399
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Multi-sensor approach towards understanding debris-flow activity in the Lattenbach catchment, Austria

Philipp Aigner1, Erik Kuschel2, Christian Zangerl2, Johannes Hübl1, Markus Hrachowitz3, Leonard Sklar4, and Roland Kaitna1
Philipp Aigner et al.
  • 1BOKU, Institute of Mountain Risk Engineering, Dept. of Civil Engineering and Natural Hazards, Vienna, Austria
  • 2BOKU, Institute of Applied Geology, Dept. of Civil Engineering and Natural Hazards, Vienna, Austria
  • 3Delft University of Technology, Civil Engineering and Geosciences, Water Resources Section, Delft, The Netherlands
  • 4Concordia University, Dept. of Geography, Planning and Environment, Montreal, Canada

Debris flows (DFs) pose a severe risk to Alpine communities and infrastructure. The Lattenbach catchment (basin area 5,3 km², relief 2134 m) in Tyrol, Austria, is an example for an active DF-site with several DFs occurring per year. To improve our understanding of the DF-process cascade in this catchment, we raise the questions: where does the sediment originate, are hillslope processes the drivers for DF-activity, and how is the relationship of rainfall amount and DF-magnitude?

We employ an approach that makes use of the data richness of this study site: High resolution ALS and TLS terrain models and aerial photographs are considered to locate significant elevation differences. Furthermore, we performed an in-detail UAV-based surveying campaign of the active channel reaches for the 2019 and 2020 DF-season. Additionally, we use datasets captured by a DF monitoring station (discharge, volume, timing, precipitation) at the catchment outlet to assess triggering rainfall as well as DF-frequency and magnitudes.

We find that in the last fifteen years up to three events occurred annually. A single location, where all DFs originate from, is not detectable, indicating a variety of sediment sources is relevant for DF-initiation, including bank failures and channel incision, partly driven by deep-seated landslides that continuously feed the channel with sediment. Between the years 2005 and 2018 the DF-volumes recorded at the catchment outlet varied between about 5.000 m³ (small) and 46.000 m³ (large). A first analysis suggests that there is a prevailing “background noise“ pattern of relatively small DF-events that happen regularly during every DF-season. We hypothesize that rare, very large events represent a tipping point in the catchment system, which leads to a period of increased large-scale DF-activity over following seasons.

How to cite: Aigner, P., Kuschel, E., Zangerl, C., Hübl, J., Hrachowitz, M., Sklar, L., and Kaitna, R.: Multi-sensor approach towards understanding debris-flow activity in the Lattenbach catchment, Austria, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15399, https://doi.org/10.5194/egusphere-egu21-15399, 2021.

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