An integrated framework for analysing horizontal and vertical tsunami evacuation. A case study of Iquique, Chile

Evacuation is a crucial method for mitigating tsunami risk. However, in many coastal areas, horizontal pedestrian evacuation may not be feasible before a tsunami arrives. In such cases, tsunami vertical-evacuation (TVE) to high-rise structures can be lifesaving. Despite its potential, TVE has received less attention compared to horizontal evacuation, particularly regarding evacuation dynamics within buildings. This article addresses this research gap and links it with previous studies on urban-scale tsunami evacuation. We developed an integrated horizontal-vertical evacuation framework using agent-based modelling, focusing on the tsunami-prone city of Iquique, Chile. Our findings indicate an overall high urban capacity for safe tsunami evacuation in Iquique, with rates of saved evacuees up to roughly 85–90 %. In critical coastal areas, TVE can reduce average effective travel times by 26 %–37 %. However, a high proportion of agents opting for TVE can increase tsunami vulnerability as the result of pedestrian density leading to reduced speeds and bottlenecks emerging around the shelters. We also examined the Terrado Cavancha Hotel, showing it can accommodate approximately 2000–3000 evacuees, with fatalities remaining below 15 % in a worst-case scenario. It takes around 20–25 min (depending on the scenario) to achieve a significant safe evacuation rate (50 % and above) within the building. Additionally, our study identifies potential indoor bottlenecks and congestion points, offering valuable insights for designers and emergency managers in planning or retrofitting buildings to enhance TVE capacities.