Preprints
https://doi.org/10.5194/nhess-2021-320
https://doi.org/10.5194/nhess-2021-320

  10 Nov 2021

10 Nov 2021

Review status: this preprint is currently under review for the journal NHESS.

Evaluating and ranking Southeast Asia's exposure to explosive volcanic hazards

Susanna F. Jenkins, Sébastien Biass, George T. Williams, Josh L. Hayes, Eleanor M. Tennant, Qingyuan Yang, Vanesa Burgos, Elinor S. Meredith, Geoffrey A. Lerner, Magfira Syarifuddin, and Andrea Verolino Susanna F. Jenkins et al.
  • Earth Observatory of Singapore, Asian School of the Environment, Nanyang Technological University, Singapore, 639754

Abstract. Regional assessments provide a large-scale comparable vision of the threat posed by multiple sources and are useful for prioritising risk-mitigation actions. There is a need for such assessments from international, regional and national agencies, industries and governments to prioritise where further study and support could be focussed. Most existing regional studies on the threat posed by volcanic activity have relied on concentric radii as proxies for hazard footprints and have focused only on population exposure, often using indices to make first-order estimates of exposure. However, this approach is an oversimplification of volcanic hazards and their associated impacts. We have developed and applied a new approach that quantifies and ranks exposure to multiple volcanic hazards for 40 high-threat volcanoes in Southeast Asia. For each of our 40 volcanoes, hazard spatial extent, and intensity where appropriate, was probabilistically modelled for four volcanic hazards across three eruption scenarios, giving 697,080 individual hazard footprints plus 19,560 probabilistic hazard outputs. We then developed a GIS framework to overlay the spatial extent of probabilistic hazard footprints with open-access datasets across five exposure categories. Finally, we used our calculated exposure values to rank each of the 40 volcanoes in terms of the threat they pose to surrounding communities. We present VolcGIS, an open-source Python code that implements all of the spatial operations required for exposure analysis, available at github.com/vharg/VolcGIS. We provide all our outputs - more than 6,500 geotif files and 70 independent estimates of exposure to volcanic hazards across 40 volcanoes - in user-friendly format. Results highlight that the island of Java in Indonesia has the highest median exposure to volcanic hazards, with Merapi consistently ranking as the highest threat volcano. Hazard seasonality, as a result of varying wind conditions affecting tephra dispersal, leads to increased exposure values during the peak rainy season (January, February) in Java, but the peak dry season (January, February, March) in the Philippines. A key aim of our study was to highlight volcanoes that may have been overlooked, perhaps because they are not frequently or recently active, but that have the potential to affect large numbers of people and assets. It is not intended to replace official hazard and risk information provided by the individual country or volcano organisations. This study and the tools developed provide a road map for future multi-source regional volcanic exposure assessments, with the possibility to extend the assessment to other geographic regions and/or towards impact and loss.

Susanna F. Jenkins et al.

Status: open (until 31 Dec 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Susanna F. Jenkins et al.

Susanna F. Jenkins et al.

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Short summary
There is a need for large-scale comparable assessments of volcanic threat, but previous approaches assume circular hazard to exposed population. Our approach quantifies and ranks five exposure types to four volcanic hazards for 40 volcanoes in Southeast Asia. Java has the highest median exposure, with Merapi consistently ranking as the highest threat volcano. This study and the tools developed provide a road map, with the possibility to extend to other regions and/or towards impact and loss.
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