Preprints
https://doi.org/10.5194/nhess-2021-74
https://doi.org/10.5194/nhess-2021-74

  30 Mar 2021

30 Mar 2021

Review status: a revised version of this preprint is currently under review for the journal NHESS.

Debris Flow event on Osorno volcano, Chile, during summer 2017: New interpretations for chain processes in the Southern Andes

Ivo Janos Fustos-Toribio1, Bastian Morales-Vargas2,3, Marcelo Somos-Valenzuela3,4, Pablo Moreno-Yaeger1,5, Ramiro Muñoz-Ramirez2, Ines Rodriguez Araneda2, and Ningsheng Chen6 Ivo Janos Fustos-Toribio et al.
  • 1Department of Civil Engineering, University of La Frontera, Francisco Salazar 1145, Temuco, Chile
  • 2Departamento de Obras Civiles y Geología, Facultad de Ingeniería, Universidad Católica de Temuco, Rudecindo Ortega 02950, Temuco, Chile
  • 3Department of Forest Sciences, Faculty of Agriculture and Forest Sciences, Universidad de La Frontera, Av. Francisco Salazar 01145, Temuco, Chile, 4780000
  • 4Butamallín Research Center for Global Change, University of La Frontera, Av. Francisco Salazar 01145, Temuco, Chile, 4780000
  • 5Department of Geoscience, University of Wisconsin–Madison, 1215 West Dayton St., Madison, WI 53706, USA
  • 6Key Laboratory of Mountain Hazards and Surface Processes, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China

Abstract. Debris flow generation on volcanic zones at the Southern Andes has not widely studied, despite the enormous economic and infrastructure damage that these events can generate. The present work contributes to the understanding of these dynamics based on a study of the 2017 Petrohué debris flow event from two complementary points of view. First, a comprehensive field survey allowed to delimitate that a rockfall initiated the debris-flow due to intense rainfall event. The rockfall lithology corresponds to lava blocks and autobrecciated lavas, predominantly over 1500 m.a.s.l. Second, the process was numerically modelled and constrained by in situ data collection and geomorphological mapping. The event was studied by back analysis using the height of flow measured in road CH-255 with errors of 5%. Debris flow volume has a high sensitivity with the initial water content in the block fall zone, ranging between 4.7x105 up to 5.5x105 m3, depending on the digital elevation model (DEM) used. Therefore, debris flow showed that the zone is controlled by the initial water content available previous to the block fall. Moreover, our field data suggest that future debris flows events can take place removing material from the volcanic edifice. We conclude that similar events could occur in the future and that it is necessary to increase the mapping of zones with autobrecciated lava close to the volcano summit. Finally, the study contributes to understanding debris flows in the Southern Andes since the Osorno volcano shares similar features with other stratovolcanoes in the region.

Ivo Janos Fustos-Toribio et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2021-74', Roberto J. Marin, 18 Apr 2021
    • AC1: 'Reply on RC1', Ivo Fustos, 03 Aug 2021
  • RC2: 'Comment on nhess-2021-74', Anonymous Referee #2, 11 Jul 2021
    • AC2: 'Reply on RC2', Ivo Fustos, 03 Aug 2021

Ivo Janos Fustos-Toribio et al.

Ivo Janos Fustos-Toribio et al.

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Short summary
Links between debris flow and volcanic evolution is an open question in the Southern Andes yet. We modeled the catastrophic debris flow using field data, geotechnical approach, and numerical modeling at the Petrohue event (Chile, 2017). Our results indicated new prone-debris flow zones. Finally, we call to consider connections between volcanoes and debris-flow in the Southern Andes.
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