Tsunami evacuation simulation considering road width in Aoshima district

Abstract

Japan is one of the countries in the world where natural disasters occur most frequently. Typhoons, earthquakes, tsunamis, volcanic eruptions, and many other natural disasters occur in Japan every year, and the risks are immeasurable. Japan is especially prone to earthquakes because of its location on the North American Plate, Eurasian Plate, Pacific Plate, and Philippine Sea Plate. Preparation for a Nankai Trough earthquake is one of the most important issues. A Nankai trough earthquake is predicted to occur with a probability of 70–80% within 30 years. Accordingly, a tsunami of more than 10 ms is expected to hit a wide area along the Pacific coast from the Kanto region to the Kyushu region, and the impact is expected to be significant. When a tsunami warning is issued, an evacuation support system that provides information on evacuation sites and routes enables faster and safer evacuation actions. In a previous study conducted in our laboratory, we proposed an evacuation support system using Low-Power Wide-Area communications and conducted a simulation to find ways to improve the evacuation support system. However, the simulation was insufficient in that it did not consider delays in evacuation completion time due to road congestion caused by limited road width, which can be expected in an actual disaster. In our current research, as an improvement to make the simulation more realistic for further developing our evacuation support system, we propose a simulation that considers road width. We examined how adoption of this simulation methodology would affect the simulation results by comparing simulations that did and did not consider road width. As a result, the proposed method showed a lower percentage of completed evacuations than the previous simulation, especially for children and the elderly. The reason for this result is that when evacuations begin simultaneously, crowding occurs as people all rush to evacuation centers. This congestion on the roads near evacuation centers prevents people from completing their evacuations. Such a phenomenon is expected to occur not only in simulations but also on actual roads. For this reason, our proposed simulation method that considers road width is a more realistic simulation. Since evacuations by car in the event of a disaster also occur, a future issue is to simulate car congestion as well. Furthermore, simulating what would happen if a disaster made a road impassable is also important.