Swiss Federal Institute for Forest, Snow and Landscape Research WSL

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Dangerous mud: debris flows

We research debris flows in various ways: we observe their behaviour via automatic monitoring stations, trigger experimental debris flows in the laboratory, and simulate their courses and spread using a computer.

Ein animiertes Schwarzweiss-Bild zeigt wie das Geschiebe eines Murgangs sich bewegt.
A debris flow is more powerful than a flood with sediment and can cause a correspondingly high amount of damage. (Image: WSL)


Understanding processes through field observation

Eine Simulation mit RAMMS::DEBRISFLOW zeigt auf einer Landkarte die möglichen Fliess- und Ausbruchswege für ein grösseres Volumen.
In 2013, the Bielzug near Herbriggen, Gde. St. Niklaus (VS) was very active. The simulations with RAMMS::DEBRISFLOW showed potential flow and break out paths for a larger volumne. (GIF: WSL)

We have set up multiple automatic debris flow monitoring stations in the Swiss Alps which provide us with important data sets for describing flow processes and for developing and calibrating numerical simulation programmes. Various measuring systems are used and tested at the stations.

An automatic debris flow monitoring station is currently in operation at the Illgraben. Other stations were installed in previous years and have also provided key data sets: Dorfbach, Schipfenbach, Preonzo, Riascio.

Debris flows occur in the Illgraben several times a year. This makes the site interesting for research. WSL has instrumented the channel with technical installations and observes the events in detail. It has also implemented a prototype system for a debris flow alarm system there.

Ein Murgang kommt den Illgraben hinunter.
Thanks to the geological structure of Illgraben, several of these events occur each year, which makes it an ideal place to study debris flows. Photo: Christoph Graf/WSL
Blick von oben auf den Illgraben bis hinunter ins Rhonetal
When it rains, the yellowish loose rock material mixes with water and becomes a slushy mass that slides into the valley as a debris flow. It also carries larger pieces of rock. Photo: Christoph Graf/WSL

Laboratory studies

At WSL's large-scale laboratory we can study the trigger, transit and deposition behaviour of debris flows on a smaller scale. In a debris flow channel, we investigate the flow behaviour of different debris flow mixtures and test measuring instruments before they are used in the field. The debris flow channel (see video "Das Ding", Diagonal 2/2017) can also be used to demonstrate the characteristic features of debris flows to visiting groups.

The debris flow laboratory at the WSL offers the possibility to investigate debris flows at a small scale. This allows scientists to study, for example, flow behavior for various natural materials, investigate debris flow impact, explore the erosion process, and test instruments before deployment in the field. The channel is also used to illustrate the debris flow process for visitors.

Application and development of simulation programmes

Numerical simulation programmes enable us to make reliable calculations of the flow behaviour of debris flows in the torrent on a debris-flow fan, which but also to identify critical conditions for overloading the torrent and indicate possible flow paths and at-risk areas outside of the torrent channel. We explore the limitations and possibilities of simulation programmes based on exemplary ample applications and devise recommendations and guidelines for their use in hazard analysis. This work is carried out within the RAMMS Rapid Mass Movements project.

Contribution of research to debris flow protection

The findings from new field data and observations, laboratory experiments and calculations with numerical simulation programmes expand the knowledge of the complex and still insufficiently known phenomenon of debris flows. In addition, they contribute to the improvement of methods and working tools for practical use in the assessment of natural hazards and form the basis for the development and assessment of protective measures.

Short video about WSL research in the Illgraben (Gottardo Pestalozzi, WSL)

Publications

Aaron J., Spielmann R., McArdell B.W., Graf C. (2023) High‐frequency 3D LIDAR measurements of a debris flow: a novel method to investigate the dynamics of full‐scale events in the field. Geophys. Res. Lett. 50(5), e2022GL102373 (10 pp.). https://doi.org/10.1029/2022GL102373Institutional Repository DORA

de Haas T., McArdell B.W., Nijland W., Åberg A.S., Hirschberg J., Huguenin P. (2022) Flow and bed conditions jointly control debris‐flow erosion and bulking. Geophys. Res. Lett. 49(10), e2021GL097611 (10 pp.). https://doi.org/10.1029/2021GL097611Institutional Repository DORA

Hirschberg J., McArdell B.W., Bennett G.L., Molnar P. (2022) Numerical investigation of sediment‐yield underestimation in supply‐limited mountain basins with short records. Geophys. Res. Lett. 49(7), e2021GL096440 (10 pp.). https://doi.org/10.1029/2021GL096440Institutional Repository DORA

McArdell B.W., Sartori M. (2021) The Illgraben torrent system. In E. Reynard (Ed.), World geomorphological landscapes. Landscapes and landforms of Switzerland. Cham: Springer. 367-378. https://doi.org/10.1007/978-3-030-43203-4_25 Institutional Repository DORA

Chmiel M., Walter F., Wenner M., Zhang Z., McArdell B.W., Hibert C. (2021) Machine learning improves debris flow warning. Geophys. Res. Lett. 48(3), e2020GL090874 (11 pp.). https://doi.org/10.1029/2020GL090874Institutional Repository DORA

Zhang Z., Walter F., McArdell B.W., de Haas T., Wenner M., Chmiel M., He S. (2021) Analyzing bulk flow characteristics of debris flows using their high frequency seismic signature. J. Geophys. Res. B. 126(12), e2021JB022755 (19 pp.). https://doi.org/10.1029/2021JB022755Institutional Repository DORA

Hirschberg J., Badoux A., McArdell B.W., Leonarduzzi E., Molnar P. (2021) Evaluating methods for debris-flow prediction based on rainfall in an Alpine catchment. Nat. Hazards Earth Syst. Sci. 21(9), 2773-2789. https://doi.org/10.5194/nhess-21-2773-2021 Institutional Repository DORA

Hirschberg J., Fatichi S., Bennett G.L., McArdell B.W., Peleg N., Lane S.N., … Molnar P. (2021) Climate change impacts on sediment yield and debris-flow activity in an alpine catchment. J. Geophys. Res. F. 126(1), e2020JF005739 (26 pp.). https://doi.org/10.1029/2020JF005739Institutional Repository DORA

Hürlimann M., Coviello V., Bel C., Guo X., Berti M., Graf C., … Yin H.Y. (2019) Debris-flow monitoring and warning: review and examples. Earth-Sci. Rev. 199, 102981 (26 pp.). https://doi.org/10.1016/j.earscirev.2019.102981Institutional Repository DORA

Meyrat G., McArdell B., Ivanova K., Müller C., Bartelt P. (2022) A dilatant, two-layer debris flow model validated by flow density measurements at the Swiss illgraben test site. Landslides. 19, 265-276. https://doi.org/10.1007/s10346-021-01733-2 Institutional Repository DORA

Mitchell A., Zubrycky S., McDougall S., Aaron J., Jacquemart M., Hübl J., … Graf C. (2022) Variable hydrograph inputs for a numerical debris-flow runout model. Nat. Hazards Earth Syst. Sci. 22(5), 1627-1654. https://doi.org/10.5194/nhess-22-1627-2022 Institutional Repository DORA

Walter F., Hodel E., Mannerfelt E.S., Cook K., Dietze M., Estermann L., … Molnar P. (2022) Brief communication: an autonomous UAV for catchment-wide monitoring of a debris flow torrent. Nat. Hazards Earth Syst. Sci. 22(12), 4011-4018. https://doi.org/10.5194/nhess-22-4011-2022 Institutional Repository DORA

Walter F., Chmiel M., Hovius N. (2022) Debris flows at Illgraben, Switzerland - from seismic wiggles to machine learning. Geomech. Tunnel. 15(5), 671-675. https://doi.org/10.1002/geot.202200039 Institutional Repository DORA

Wenner M., Allstadt K., Thelen W., Lockhart A., Hirschberg J., McArdell B.W., Walter F. (2022) Seismometer records of ground tilt induced by debris flows. Bull. Seismol. Soc. Amer. 112(5), 2376-2395. https://doi.org/10.1785/0120210271 Institutional Repository DORA

Projects

Surrogate bedload transport measurements with the Swiss plate geophone system

This project aims to further develop the Swiss plate geophone system, a passive seismic method to measure bedload transport in water courses, with a new set of controlled experiments and field calibration measurements.

CCES-TRAMM: Triggering of Rapid Mass Movements in Steep Terrain

TRAMM was a research project of the ETH Competence Centre of Environment and Sustainability (CCES) from 2006 to 2015 with the aim to better understand mechanisms of rapid mass movements.

WSL strategic initiative: Climate Change Impacts on Alpine Mass Movements (CCAMM) 

Past projects:

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