Tsunami risk perception and evacuation strategy. A case study in lisbon.

The tsunamis resulting from the earthquakes of 2004 (Sumatra), 2010 (Chile), 2011 (Tohoku), or 2015 (Chile) caused more than 250,000 deaths and damage to both the built and natural environments, some of which is irreparable. However, they also triggered a global awareness of the combined earthquake-tsunami risks. Awareness must be accompanied by actions that foster preparedness and response capacity — a principle enshrined in the Sendai Framework. In this context, structures for public warnings have been created in Lisbon. Specific programmes to promote resilience have been launched, and the revision of the Municipal Master Plan (PDM) provided the framework for generating tsunami inundation maps. This work presents the principles and methods leading to the calculation of the extent of tsunami-inundated areas following an earthquake with the same magnitude as that of 1755, describes risk awareness and risk communication measures undertaken, including risk perception initiatives and presents simulations of evacuation scenarios for Lisbon’s waterfront, taking in consideration the inundation time line, building-related vulnerability and the proposed evacuation meeting points.

Vulnerability associated to risk perception can be reduced by increasing the quality of information on tsunami propagation, evacuation routes, and safe meeting points. The perception of Lisbon’s population regarding tsunami risk, self-protection behaviours, and knowledge of exposed and safe zones is shown to be ambiguous – good knowledge about the phenomenon does not translate into adequate self-protection response. The simulation platform for the evacuation of Lisbon's waterfront areas, based on social forcing concepts, was specifically employed to provide data to discuss the impact of information previously received by the population on evacuation quantifiers, including the inundation timeline and maximum extent, and the most adequate routes. The evacuation simulations allowed to understand to what extent information and awareness-raising actions contribute to increased risk perception and self-protection behaviours and the increase of survival rates.

Acknowledgement: This works was supported by the Portuguese Foundation for Science and Technology (FCT) through research centre CERIS UIDB/04625/2020