The primary objective of tsunami disaster mitigation is to reduce the casualties. The major cause of the deaths is drowning by tsunami current, especially during evacuation. In the paper, the causes of deaths are discussed through reference to past experiences. A fault tree is presented to summarize the physical danger posed by tsunami waves to the human body, and the personal danger is discussed based on the tree. The stability of the human body against wave front collision and tsunami currents is discussed and threshold conditions are proposed. The time for evacuation is usually very limited and the risk of encountering a tsunami during evacuation is often high. Walking in inundated areas during a tsunami attack is especially dangerous. Vertical evacuation is highly recommended.
