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Quantifying cascading impacts through road network analysis in an insular volcanic setting: the 2021 Tajogaite eruption of La Palma Island (Spain)

Lucia Dominguez1, Sébastien Biass1, Corine Frischknecht1, Alana Weir1, Maria Paz Reyes-Hardy1, Luigia Sara Di Maio1, Nemesio Pérez2,3, and Costanza Bonadonna1

  • Affiliations: 1Department of Earth Sciences, University of Geneva, Geneva, 1205, Switzerland 2Instituto Volcanológico de Canarias (INVOLCAN), San Cristóbal de La Laguna, 38320, Spain 3Instituto Tecnológico y de Energías Renovables (ITER), Granadilla de Abona, 38600, Spain 

  • Presentation type: Talk

  • Presentation time: Friday 09:00 - 09:15, Room S160

  • Programme No: 6.7.3

  • Theme 6 > Session 7

Abstract

Post-event impact assessments (PEIA) are fundamental to elucidate the drivers of disasters and better anticipate the impacts from future events. The 2021 Tajogaite eruption of Cumbre Vieja (La Palma, Spain) demonstrated the various orders of impact due to compound volcanic products (i.e., lava, tephra, gas) affecting a highly interconnected and low redundant infrastructure, typical of insular environments. Using a forensic approach, we discretise the causal order of cascading impacts, from physical damage (first order) to loss of functionality of the road network (second order) and subsequent systemic disruption of emergency management and socio-economic sectors (third order). Based on graph theory, we apply a comprehensive road network analysis to quantify the loss of functionality and resulting effects on driving time syn- and post-eruption. Loss of functionality is based on the spatiotemporal evolution of connectivity using centrality indicators, calculated for all road segments. The consequences on dependent systems are expressed in terms of increased driving time between target locations for emergency (evacuation), public health (hospital), agriculture (crops-market), and education (schools). Graph indicators are objective measures of road system performance both during (disturbing and degraded states) and after the eruption (restorative phase), when two new roads where rapidly built to reconnect the northwest and southwest of La Palma island. This study demonstrates how network analyses, informed by comprehensive PEIA, can accurately capture complex systemic disturbances of infrastructures, thus highlighting its potential for risk assessments.