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Are cities becoming increasingly threatened by volcanic hazards?

Elinor Meredith1, Rui Xue Natalie Teng2, Susanna Jenkins2, Josh Hayes3, Sébastien Biass4, Eleanor Tennant2, Heather Handley^1,5 ^

  • Affiliations: 1ITC Faculty, University of Twente, Enschede, the Netherlands; 2Earth Observatory of Singapore, Asian School of the Environment, Nanyang Technological University, Singapore; 3GNS Science, Lower Hutt, New Zealand; 4Department of Earth Sciences, University of Geneva, Geneva, Switzerland; 5School of Earth, Atmosphere and Environment, Monash University, Clayton, Australia 

  • Presentation type: Talk [Invited]

  • Presentation time: Friday 08:30 - 08:45, Room S160

  • Programme No: 6.7.1

  • Theme 6 > Session 7

Abstract

City expansion near volcanoes exposes dense concentrations of people, buildings, and infrastructure to volcanic hazards. Identifying key cities at risk and quantifying the rates of city population expansion on different scales can inform targeted research, mitigation, and land-use planning efforts. We rank 1,106 cities globally based on their exposure within 100 km to 596 Holocene volcanoes, considering population counts, proximity to volcanoes, and the number of nearby volcanoes. Notably, 50% of people currently living within 100 km of a volcano are in cities, with some exposed to multiple volcanoes. Over 8 million people in Bandung, Indonesia, live within 30 km of up to 12 volcanoes. Building on these rankings, we assess urban expansion and population growth between 1975 and 2020, using data at 5-year intervals and future projections between 2030 and 2070 at 10-year intervals. We show that, on average, city margins are spreading towards volcanoes. We also show the rate of increase in city population density towards volcanoes. However, for some countries, such as El Salvador, Japan, or the Philippines, where >70% of land is exposed to volcanic hazards, there are limits on the availability of safer areas for expansion. Using city case studies, we assess directions of city expansion and relate these to potential volcanic flow directions and wind directions to identify critical areas for more localised assessment and mitigation efforts. Our research provides a framework for global and localised assessment of spatio-temporal city population trends, highlighting the increased exposure and need for targeted mitigation efforts.