Nat. Hazards Earth Syst. Sci., 20, 505–520, 2020 https://doi.org/10.5194/nhess-20-505-2020 © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License. Back calculation of the 2017 Piz Cengalo–Bondo landslide cascade with r.avaflow: what we can do and what we can learn Martin Mergili1,2, Michel Jaboyedoff3, José Pullarello3, and Shiva P. Pudasaini4 1Institute of Applied Geology, University of Natural Resources and Life Sciences (BOKU), Peter-Jordan-Straße 82, 1190 Vienna, Austria 2Geomorphological Systems and Risk Research, Department of Geography and Regional Research, University of Vienna, Universitätsstraße 7, 1010 Vienna, Austria 3Institute of Earth Sciences, University of Lausanne, Quartier UNIL-Mouline, Bâtiment Géopolis, 1015 Lausanne, Switzerland 4Institute of Geosciences, Geophysics Section, University of Bonn, Meckenheimer Allee 176, 53115 Bonn, Germany Correspondence: Martin Mergili (
[email protected]) Received: 26 June 2019 – Discussion started: 8 July 2019 Revised: 20 December 2019 – Accepted: 16 January 2020 – Published: 21 February 2020 Abstract. In the morning of 23 August 2017, around 3 × produced with an enhanced version of the two-phase mass 106 m3 of granitoid rock broke off from the eastern face of flow model (Pudasaini, 2012) implemented with the simu- Piz Cengalo, southeastern Switzerland. The initial rockslide– lation software r.avaflow, based on plausible assumptions of rockfall entrained 6×105m3 of a glacier and continued as a the model parameters. However, these simulation results do rock (or rock–ice) avalanche before evolving into a channel- not allow us to conclude on which of the two scenarios is ized debris flow that reached the village of Bondo at a dis- the more likely one.