An allocating method of tsunami evacuation routes and refuges for minimizing expected casualties

In an event of tsunami inundation, it is usually advised to take the closest refuge with the shortest route. However, a detour which avoids inundation may earn a longer time for safe evacuation than taking the shortest route. Careful and strategic planning of the allocation of refuges and route selection would provide the maximum survivability to residents. This study aims to develop an allocation method for refuges and evacuation routes to reduce the number of casualties for all tsunami scenarios. The system allocates a refuge and an evacuation route to each of residents prior to the occurrence of an earthquake with incorporating many possible tsunamis. More specifically, this model calculates the length of time left for safe evacuation for various combinations of refuges and routes for each evacuee. A combination that gives the maximum of this time is selected for each evacuee and an evacuation plan for all evacuees is obtained. This process is repeated for other possible tsunami scenarios. Evacuation simulations are performed for all obtained plans with other tsunami scenarios and the number of casualties are counted. An evacuation plan which gives the minimum number of accumulated casualties is chosen as the optimal plan. Validation simulations for a town revealed that the method was effective in all tested cases and reduced casualties by approximately 40% on average. It should be noted here that this optimal plan is identical for all tsunami scenarios. The optimal plan is characterized based on a tsunami scenario with large, rapid inundation in the study area. This indicates that we can get optimal plan with a specified scenario before a disaster occurrence when conducting similar examination in other areas.