Tomoyuki Takabatake

EFFECT OF SEA LEVEL RISE AND INCREASE IN TYPHOON INTENSITY ON COASTAL STRUCTURES IN TOKYO BAY

Sea level rise and an increase in typhoon intensity are two of the results expected from future climate change. In the present work a methodology to change the intensity of tropical cyclones in Japan is developed based on the work of Knutson and Tuleya (2004). An example of how this would affect one of the worst typhoons to hit the Tokyo Bay area in the 20 century was thus developed, highlighting the considerable dangers associated with this event, and how current sea defences could be under danger of failing by the end of the 21 century.

Advanced casualty estimation based on tsunami evacuation intended behavior: case study at Yuigahama Beach, Kamakura, Japan

Tsunamis are some of the most destructive types of natural hazards that can affect coastal areas. To optimize tsunami mitigation measures, it is important to estimate the potential casualties that can result from one of these events. Taking into account tsunami awareness and the possible evacuation behavior of at-risk individuals is necessary to estimate the number of casualties, though most of the research carried out to date has not considered detailed evacuation behavior when conducting simulations. In the present study, the authors proposed a new approach to estimating the number of tsunami casualties, based on a tsunami evacuation simulation model that considers the evacuation behavior of local residents, tourists and beach users. Such behavior parameters were incorporated by analyzing the results from previous questionnaires surveys. The model was applied to Yuigahama Beach in Kamakura City, Japan, with the aim of assessing potential tsunami casualties and providing suggestions regarding tsunami mitigation measures. The authors conducted seven tsunami inundation simulations for different earthquake scenarios, and then casualties were estimated considering six different evacuation scenarios. Based on the simulation results, it appears particularly important to attempt to improve the intended evacuation behavior of both the local population and visitors. Particularly, providing information about safe places and the routes to reach them is necessary, as prompt evacuation and heading to higher ground were found to be insufficient behavior to save lives during a tsunami event.

An Experimental Study on Resistance of Coastal Dike with Lean Cement Mixed Soil

The tsunami generated by the 2011 off the pacific coast of tohoku earthquake caused massive damage to coastal dikes. It is required for coastal dikes to increase the resistance of tsunami. Although some coastal dikes resistant to tsunami are proposed, embankment materials which can enhance the resistance of coastal dikes are not identified clearly. In this study, embankment materials of a coastal dike which can enhance its resistance are investigated by conducting hydraulic physical model tests. The results of hydraulic tests showed that embankment mixed by cement or clay could enhance the resistance of tsunami. The numerical simulation was also conducted to clarify the erosion process of lean cement mixed soil.