Tsunami risk hazard in Tokyo Bay: The challenge of future sea level rise

Sea level rise is one of the major challenges facing humanity in the 21st century, and could compound the risks posed by tsunamis to coastal cities. The authors conducted computer simulations of tsunami inundation and propagation into Tokyo Bay, and analysed the risks that such events pose to the cities of Yokohama and Kawasaki, for different sea level rise scenarios . The results show that unless significant investment in improved coastal defences is made, the area that can potentially be flooded by such events will gradually increase in the course of the 21st century. However, the risk to the life of the inhabitants of these cities will broadly remain unchanged until sea levels become +1.0 m higher than at present. From then, the risk of casualties taking place will rapidly increase, as the depth and velocity of the tsunami wave will substantially rise. Such results provide some indication regarding the long-term planning strategy to manage coastal defences around Tokyo Bay, highlighting the need to eventually reinforce coastal defences and the important contribution of tsunami evacuation to minimize casualties during such events.