Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2017-626
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
01 Nov 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Hydrology and Earth System Sciences (HESS).
The temporally varying roles of rainfall, snowmelt and soil moisture for debris flow initiation in a snow dominated system: the compound trigger concept
Karin Mostbauer1, Roland Kaitna1, David Prenner1, and Markus Hrachowitz2 1Institute of Mountain Risk Engineering, University of Natural Resources and Life Sciences, Vienna, Austria
2Water Resources Section, Faculty of Civil Engineering and Geosciences, Delft University of Technology, the Netherlands
Abstract. Debris flows represent a severe hazard in mountain regions. Though significant effort has been made to predict such events, the trigger conditions as well as the hydrologic disposition of a watershed at the time of debris flow occurrence are not well understood. Traditional intensity-duration threshold techniques to establish trigger conditions generally do not account for distinct influences of rainfall, snowmelt, and antecedent moisture. To improve our knowledge on the connection between debris flow initiation and the hydrologic system and to overcome the above limitations, this study explores the use of a semi-distributed conceptual rainfall-runoff model, linking different system variables such as soil moisture, snowmelt, or runoff with documented debris flow events in the inner Pitztal watershed, western Austria. The model was run on a daily basis between 1953 and 2012. Analyzing a range of modelled system state and flux variables at days on which debris flows occurred, three distinct dominant trigger mechanisms could be clearly identified. While the results suggest that for 68 % (17 out of 25) of the observed debris flow events during the study period high-intensity rainfall was the dominant trigger, snowmelt was identified as dominant trigger for 24 % (6 out of 25) of the observed debris flow events. In addition, 8 % (2 out of 25) of the debris flow events could be attributed to the combined effects of low-intensity, long-lasting rainfall and transient storage of this water, causing elevated antecedent soil moisture conditions. The results also suggest a relatively clear temporal separation between the distinct trigger mechanisms, with high-intensity rainfall as trigger being limited to mid- and late summer. The dominant trigger in late spring/early summer is snowmelt. Based on the discrimination between different modelled system states and fluxes and more specifically, their temporally varying importance relative to each other, rather than their absolute values, this exploratory study demonstrates that already the use of a relatively simple hydrological model can prove useful to gain some more insight into the importance of distinct debris flow trigger mechanisms in a compound trigger concept, highlighting in particular the relevance of snowmelt contributions and the switch between mechanisms in early- to mid-summer in snow dominated systems.

Citation: Mostbauer, K., Kaitna, R., Prenner, D., and Hrachowitz, M.: The temporally varying roles of rainfall, snowmelt and soil moisture for debris flow initiation in a snow dominated system: the compound trigger concept, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2017-626, in review, 2017.
Karin Mostbauer et al.
Karin Mostbauer et al.
Karin Mostbauer et al.

Viewed

Total article views: 252 (including HTML, PDF, and XML)

HTML PDF XML Total Supplement BibTeX EndNote
213 36 3 252 7 2 3

Views and downloads (calculated since 01 Nov 2017)

Cumulative views and downloads (calculated since 01 Nov 2017)

Viewed (geographical distribution)

Total article views: 252 (including HTML, PDF, and XML)

Thereof 246 with geography defined and 6 with unknown origin.

Country # Views %
  • 1

Saved

Discussed

Latest update: 19 Nov 2017
Publications Copernicus
Download
Short summary
Debris flows represent a severe hazard in mountain regions and so far remain difficult to predict. We applied a hydrological model to link not only precipitation, but also snowmelt, antecedent soil moisture, etc. with debris flow initiation in an alpine watershed in Austria. Our results highlight the value of this more holistic perspective, i.e. a compound trigger concept, for developing a better understanding for debris flow initiation.
Debris flows represent a severe hazard in mountain regions and so far remain difficult to...
Share