20 Jul 2023
 | 20 Jul 2023
Status: this preprint is open for discussion.

Scenario building and runout modelling for debris flow hazards in pro-/periglacial catchments with scarce past event data: application of a multi-methods approach for the Dar catchment (western Swiss Alps)

Mauro Fischer, Mario Kummert, Reto Aeschbacher, Christoph Graf, Alexis Rüeger, Philippe Schoeneich, Markus Zimmermann, and Margreth Keiler

Abstract. In high mountain areas, the disposition (susceptibility of occurrence) for debris flows is increasing in steep terrain, as – due to climate change – rapid glacier retreat and permafrost degradation is favouring higher availability of loose sediments. The probability of occurrence and magnitude of pro- and periglacial debris flows is increasing, too, as triggering events such as heavy thunderstorms, long-lasting rainfalls, intense snow melt or rain-on-snow events are likely to occur more often and more intensely in future decades. Hazard assessment for debris flows originating from pro- and periglacial areas is thus crucial but remains challenging, as records of past events on which local magnitude-frequency relationships and debris flow scenarios can be based on are often scarce or inexistent. In this study, we present a multi-methods approach for debris flow hazard scenario building and runout modelling in pro- and periglacial catchments with scarce past event data. Scenario building for the debris flow initiation zone reposes on (i) the definition of meteorological and hydrological triggering scenarios using data on extreme point rainfall and precipitation-runoff modelling, and (ii) the definition of bed load scenarios from empirical approaches and field surveys. Numerical runout modelling and hazard assessment for the resulting debris flow scenarios is carried out using RAMMS-DF, which was calibrated to the studied catchment (Le Dar, western Swiss Alps) based on the area of debris flow deposits from the single major event recorded there in summer 2005. The developed approach is among the first to propose systematic scenario building for pro- and periglacial debris flows triggered by precipitation dependent events.

Mauro Fischer et al.

Status: open (until 08 Oct 2023)

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  • RC1: 'Comment on egusphere-2023-1190', Stefan Hergarten, 06 Sep 2023 reply

Mauro Fischer et al.

Mauro Fischer et al.


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Short summary
Due to climate change, the hazard for debris flows originating in glacier forefields or areas dominated by seasonal to perennial frost is increasing. Hazard assessment for this type of debris flows is especially difficult as records of past events are typically scarce or inexistent. We therefore developed a multi-methods approach for scenario building and runout modelling for pro- and periglacial debris flows triggered by precipitation events and applied it to a catchment in the Swiss Alps.