Towards a Proactive Risk Mitigation Strategy at La Fossa Volcano, Vulcano Island

Friday, 19 December 2014
Sebastien Biass1, Chris E. Gregg2, Corine Frischknecht1, Jean-Luc Falcone3, Pierino Lestuzzi4, Federico di Traglia5, Mauro Rosi6 and Costanza Bonadonna1, (1)University of Geneva, Section of Earth and Environmental Sciences, Geneva, Switzerland, (2)East Tennessee State University, Department of Geosciences, Johnson City, TN, United States, (3)University of Geneva, Department of Computer Science, Geneva, Switzerland, (4)EPFL, ENAC IIC IMAC, Lausanne, Switzerland, (5)University of Florence, Dipartimento di Scienze della Terra, Florence, Italy, (6)Italian Civil Protection, Roma, Italy
A comprehensive risk assessment framework was built to develop proactive risk reduction measures for Vulcano Island, Italy. This framework includes identification of eruption scenarios; probabilistic hazard assessment, quantification of hazard impacts on the built environment, accessibility assessment on the island and risk perception study. Vulcano, a 21 km2 island with two primary communities host to 900 permanent residents and up to 10,000 visitors during summer, shows a strong dependency on the mainland for basic needs (water, energy) and relies on a ~2 month tourism season for its economy. The recent stratigraphy reveals a dominance of vulcanian and subplinian eruptions, producing a range of hazards acting at different time scales. We developed new methods to probabilistically quantify the hazard related to ballistics, lahars and tephra for all eruption styles. We also elaborated field- and GIS- based methods to assess the physical vulnerability of the built environment and created dynamic models of accessibility.

Results outline the difference of hazard between short and long-lasting eruptions. A subplinian eruption has a 50% probability of impacting ~30% of the buildings within days after the eruption, but the year-long damage resulting from a long-lasting vulcanian eruption is similar if tephra is not removed from rooftops. Similarly, a subplinian eruption results in a volume of 7x105 m3 of material potentially remobilized into lahars soon after the eruption. Similar volumes are expected for a vulcanian activity over years, increasing the hazard of small lahars. Preferential lahar paths affect critical infrastructures lacking redundancy, such as the road network, communications systems, the island’s only gas station, and access to the island’s two evacuation ports. Such results from hazard, physical and systemic vulnerability help establish proactive volcanic risk mitigation strategies and may be applicable in other island settings.