Preprints
https://doi.org/10.5194/nhess-2020-394
https://doi.org/10.5194/nhess-2020-394

  11 Dec 2020

11 Dec 2020

Review status: a revised version of this preprint was accepted for the journal NHESS and is expected to appear here in due course.

Lava flow hazard map of Piton de la Fournaise volcano

Magdalena Oryaëlle Chevrel1, Massimiliano Favalli2, Nicolas Villeneuve3,4,5, Andrew J. L. Harris1, Alessandro Fornaciai2, Nicole Richter3,5,6, Allan Derrien3,5, Patrice Boissier3,5, Andrea Di Muro3,5, and Aline Peltier3,5 Magdalena Oryaëlle Chevrel et al.
  • 1Université Clermont Auvergne, CNRS, IRD, OPGC, Laboratoire Magmas et Volcans, F-63000 Clermont-Ferrand, France
  • 2Istituto Nazionale di Geofisica e Vulcanologia (INGV), Via Battisti, 53, 56125 Pisa, Italy
  • 3Université de Paris, Institut de physique du globe de Paris, CNRS, F-75005 Paris, France
  • 4Université de La Réunion, Laboratoire Géosciences Réunion, F-97744 Saint-Denis, France
  • 5Observatoire Volcanologique du Piton de la Fournaise, Institut de physique du globe de Paris, F-97418 La Plaine des Cafres, France
  • 6Helmholtz Centre Potsdam, German Research Centre for Geosciences (GFZ), Telegrafenberg, Potsdam, 14473, Germany

Abstract. Piton de la Fournaise, situated on La Réunion Island (France), is one of the most active hot spot basaltic shield volcanoes worldwide, experiencing at least two eruptions per year since the establishment of the observatory in 1979. Eruptions are typically fissure-fed and form extensive lava flow fields. About 95 % of some ~250 historical events (since the first confidently dated eruption in 1708) have occurred inside an uninhabited horse-shoe shaped caldera (hereafter referred to as the Enclos) which is open to the ocean on its eastern side. Rarely (12 times since the 18th century), fissures have opened outside of the Enclos where housing units, population centers and infrastructure are at risk. In such a situation, lava flow hazard maps are a useful way of visualizing lava flow inundation probabilities over large areas. Here, we present a lava flow hazard map for Piton de la Fournaise volcano based on: i) vent distribution, ii) statistics of lava flow lengths, iii) lava flow recurrence times, and iv) simulations of lava flow paths across multi-temporal (i.e., regularly updated) topography using the DOWNFLOW stochastic numerical model. A map of the entire volcano highlights that the most probable (up to 12 %) location for future lava flow inundation is within the Enclos, where about 100,000 visitors are present each year. Hazard distribution changes throughout the analysis period due to the high frequency of eruptions that constantly modifies the vent opening distribution as well as the topography and the lava flow dimensional characteristics. Outside of the Enclos, probabilities reach 0.5 % along the well-defined rift zones and, although hazard occurrence in inhabited areas is deemed to be very low (< 0.1 %), it may be underestimated here, as our study is only based on post-18th century records and neglects cycles of activity at the volcano. Specific hazard maps considering different event scenarios (i.e., events fed by different combinations of temporally evolving superficial and deep sources) are required to better assess affected areas in the future – especially by atypical, but potentially extremely hazardous, large volume eruptions. At such an active site, our method supports the need for regular updates of DEMs and associated lava flow hazard maps if we are to be effective in mitigating the associated risks.

Magdalena Oryaëlle Chevrel et al.

 
Status: closed
Status: closed
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Magdalena Oryaëlle Chevrel et al.

Magdalena Oryaëlle Chevrel et al.

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Short summary
Piton de la Fournaise is one of the most active basaltic shield volcanoes worldwide. Eruptions are typically effusive and form lava flows. Most historical events have occurred inside an uninhabited caldera but rarely lava have flowed where population and infrastructure might be at risk. We present an up-to-date lava flow hazard map to visualize the probability of inundation by a lava flow per unit area that is an essential tool for hazard mitigation and guiding crises response management.
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