Abstract
While a landslide at the volcanic island of Stromboli (Aeolian Islands, Italy) in December 2002 created a tsunami with a run-up of 10.9 m, two paroxysmal eruptions in the summer of 2019 caused a tsunami with an amplitude of 40 to 20 cm. All three events required rapid, spontaneous emergency evacuations of the beach zone as the time between tsunami generation and impact is around 4 min. These conditions thus require a special consideration of the issue of evacuation capabilities on the island in the event of a volcanogenic tsunami. The purpose of this paper is thus to (i) determine pedestrian evacuation times from high-risk coastal areas to safe zones, (ii) to assess building evacuation ease, and (iii) determine emergency evacuation plans (for buildings and coastal zones). For this purpose, we created a GIS-based risk analysis/mapping tool that also allowed macroscopic evacuation modelling. In our case, the high-risk zone to be evacuated involves an area extending to 10 m a.s.l. and involving 123 individual buildings over an area of 0.18 km2. The results show that 33% of the buildings can be evacuated in 4 min, and that a 10-min warning time is required for a complete and well-distributed evacuation whereby the population is evenly distributed between all evacuation exits to avoid the potential for congestion. Initial interviews of residents in the at-risk zone reveal a high level of awareness and a desire for personalized evacuation scenarios.
Highlights
All international tsunami risk management bodies agree that planning for evacuation drastically reduces the risk and saves lives among coastal populations (Scheer et al 2011; FEMA 2019)
A safety margin should be added between the area likely to be flooded and the refuge area to guarantee the safety of individuals in the event of extreme events (Péroche 2016), where Leone et al (2018) in their EXPLOIT method advise a safety margin of at least 5 m above the maximum run-up recorded
Because our initial objective is to set-up, fine tune and test the methodology, we focused on a single control zone which contained all key elements of the evacuation scenario, and which is representative of the Geographical Information System (GIS) content for the entire risk zone
Summary
All international tsunami risk management bodies agree that planning for evacuation drastically reduces the risk and saves lives among coastal populations (Scheer et al 2011; FEMA 2019). The first step of an evacuation planning approach based on macroscopic modelling is to collect as much information as possible on the tsunami risk in the target area (Scheer et al 2011; FEMA 2019) Fundamental to this is a definition of the exposed area, i.e., the area likely to be flooded by the tsunami and in need of evacuation, and a safe “refuge” area (cf Leone et al 2018; Fig. 1). We here develop just such a method, based on the models of Péroche (2016) and Leone et al (2018), to assess best horizontal pedestrian evacuation from a populated shoreline in the event of a locally-induced volcanogenic tsunami for which there is little response time
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