Assessment of Tsunami Evacuation Plan in Small Declining Cities: Study Case of Tosashimizu, Japan

Cities witnessing quick population shrinkage may not be able to afford to build and maintain coastal protection structures against severe tsunamis and thus rely more on efficient evacuation plans to save their population. Focusing on the Misaki area in Tosashimizu in Kochi prefecture as a case study site, we conducted a tsunami and evacuation simulation to reproduce the behaviour of an ageing population and assess the current city evacuation policy. We computed the tsunami propagation and inundation based on nonlinear shallow equations coupled with a 1D-open-channel flow model to represent tsunami runup through rivers. The evacuation simulation implemented the shortest-path decision model. To accurately describe evacuation behaviours, we divided the population into three groups: able or disabled-bodied inhabitants and tourists and reduced the walking speed according to the road’s slope. Results show that the tsunami may arrive earlier due to the consideration of the tsunami penetration through rivers and waterways. While all able-bodied locals can reach their evacuation spot safely, some disabled-bodied persons cannot.