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Debris flows at Ritigraben: magnitude, frequency, channel activity and triggering weather conditions (Valais Alps)

Based on 2450 increment cores, the debris-flow frequency has been assessed on the Ritigraben cone (15702005) and the number of events extended from ten events known from archives to 123 events. The study also allowed putting the apparent increase in the frequency of debris-flow events in the late 20th century into a larger context and showed that debris flows occurred even more frequently in the past than they do today, especially during the 19th century.

A comparison of debris-flow data with chronicle data of neighboring rivers showed that large-scale events with extended flooding affecting most parts of the southern Swiss Alps (e.g., september 1993) have repeatedly occurred in the past as well.

The spatial distribution of trees affected on the cone during past events finally indicates that the largest event known for the Ritigraben (1993; ca. 60'000 m³) cannot be considered a unique event.

 

 
     
 

Project applicants: Swiss Federal Office for Water and Geology (FOWG); Forest and Landscape Authority of the Canton of Valais; Road and River Engineering Authority of the Canton of Valais; Grächen and St. Niklaus communities

Contact: Markus Stoffel

Publications :

Stoffel, M., Bollschweiler, M., Beniston, M. (2011): Rainfall characteristics for periglacial debris flows in the Swiss Alps: past incidences – potential future evolutions. Climatic Change 105: 263-280 [PDF]

Lugon, R., Stoffel, M. (2010): Rock-glacier dynamics and magnitude–frequency relations of debris flows in a high-elevation watershed: Ritigraben, Swiss Alps. Global and Planetary Change 73: 202–210. [PDF]

Stoffel, M. (2010): Magnitude-frequency relationships of debris flows – a case study based on field surveys and tree-ring records. Geomorphology. 116: 67–76. [PDF]

Stoffel, M. (2008): On the evolution of debris-flow occurrence in space and time – results from tree-ring analyses. Proceedings of the International Conference “Debris Flows: Disasters, Risk, Forecast, Protection”. Pyatigorsk, Russia, 22-29 September 2008, pp. 125–128. [PDF]

Stoffel, M. (2008): Murgangaktivität auf einem bewaldeten Kegel der Schweizer Alpen seit dem späten Holozän. Lehren aus der Vergangenheit – Auswirkungen für die Zukunft. Proceedings 11th Interpraevent Congress 2008, May 26 – 30, 2008. Dornbirn, Austria. Vol. 1 : 501–511. [PDF]

Stoffel, M. (2007): Debris-flow activity in the Ritigraben torrent (Valais Alps, Switzerland): will there be less but bigger events in a future greenhouse climate? McInnes, R., Jakeways, J., Fairbank, H., Mathie, E. (eds.) Landslides and climate change: challenges and solutions. Taylor & Francis Group, London UK: 51–58. [PDF]

Stoffel, M., Conus, D., Grichting, M.A., Lièvre, I., Maître, G. (2008): Unraveling the patterns of late Holocene debris-flow activity on a cone in the central Swiss Alps: chronology, environment and implications for the future. Global and Planetary Change 60: 222–234 [PDF].

Stoffel, M., 2006. Estimating magnitude-frequency relationships for debris flows on forested cones – working co.ncept and preliminary results. Proceedings International Symposium Interpraevent “Disaster Mitigation of Debris Flows, Slope Failures and Landslides”, September 25–27, 2006, Niigata, Japan. Universal Academic Press, Tokyo, pp. 159–165. [PDF]

Stoffel, M., Beniston, M., 2006. On the incidence of debris flows from the early Little Ice Age to a future greenhouse climate: a case study from the Swiss Alps. Geophysical Research Letters 33, L16404. [PDF]

Stoffel, M., Lièvre, I., Conus, D., Grichting, M.A., Raetzo, H., Gärtner, H.W. & Monbaron, M. (2005): 400 years of debris flow activity and triggering weather conditions: Ritigraben VS, Switzerland . Arctic, Antarctic and Alpine Research 37(3): 387395. [PDF]

Stoffel, M., Lièvre, I, Conus, D., Grichting, M., Gärtner, H. & Monbaron, M. (2004): Rekonstruktion der Muraktivität im Ritigraben (VS) und Vergleich mit Chronikdaten benachbarter Gewässer. Mitteilungen der VAW 184: 25-40. [PDF]

Stoffel, M., Gärtner, H., Lièvre, I. & Monbaron, M. (2003): Comparison of reconstructed debris flow event years (Ritigraben, Switzerland) and existing flooding data in neighboring rivers. In: Rickenmann D. & Chen, C. (eds.): Debris Flow Hazard Mitigation: Mechanics, Prediction, and Assessment 1: 243-253. [offprints]

 

 
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