Simulation of tsunami evacuation behavior considering inland direction

Many lives have been lost in various earthquakes and tsunami disasters around the world. In Japan, future earthquakes originating in the Nankai Trough and Hyuga-nada Sea are expected to cause strong tremors and large tsunamis over a wide area along the Pacific coast. Previous tsunami evacuation studies have considered only the distance to the nearest evacuation facility and the need to evacuate to higher ground outside the inundation zone in their simulations. However, tsunami evacuees rarely evacuate toward the sea, even to reach a nearby evacuation facility, because of the counterintuitive nature such movement. In this study, we accordingly conducted agent-based tsunami evacuation simulations in Takanabe town, Miyazaki Prefecture, to compare the evacuation ratio when agents evacuated to their nearest facility regardless of direction with that when they evacuated to their nearest inland facility. The results showed that the evacuation to the inland facilities took more time to complete early in the evacuation process than the evacuation to the nearest facilities. Furthermore, the evacuation to the inland facilities resulted in large differences in the number of evacuees at some evacuation facilities compared to the evacuation to the nearest facilities. It is therefore necessary to consider the direction of the coastline when planning tsunami evacuations.