Tsunami Bōsai
Building Coastal Resilience in South Izu Peninsula

Evellyn Tan

Miho Mazereeuw

Caitlin Mueller
Cristina Parreño
Bōsai is a Japanese term," Bo" meaning prevention and "Sai" disaster, commonly associated with disaster preparedness and the necessary actions against such catastrophic events. In Japan, Bōsai is critically embedded in the Japanese culture, where children learn it in school from an early age. It is also regularly promoted in public by the government as a reminder for citizens to stay vigilant against disasters. Embedding preparedness for disasters to citizens on a daily basis is a significant effort to build the nation's social resilience against disasters.

Located in the Circum-pacific of "Ring of Fire" and surrounded by sea, Japan, with an extreme range of topographic and geomorphological landscape, is highly prone to disasters. The south coastal belt of the islands is incredibly vulnerable to mega-tsunamis as the country is situated at the collision plate forming active troughs capable of generating forcefully destructive tsunami waves. The Great East Japan Earthquake that hit the Tohoku region in 2011 exposed disaster planning challenges and a looming demographic crisis in Japanese coastal towns. In the face of a disaster, many vulnerable elderly living in super-aging coastal towns struggled to evacuate to higher grounds in time before the first wave arrived. Statistically, 1 in 3 residents in the areas worst hit by the disaster is aged more than 65 years old, a significantly higher ratio than the national average of 23 percent of the elderly population.

Despite the elaborate network of tsunami barriers constructed by the government to protect the coasts, many coastal settlements will still be significantly affected by L1 tsunamis of 10 meters or higher in the future. Thus, further building disaster-resilient capacity of social and ecological ecosystems against tsunamis is vital to the survival of lives and livelihood of Japan's coast. This thesis highlights the importance of socio-ecological design strategies of coastal towns through: improving urban connectivity of coastal forest as coastal hydraulic barriers, increasing porosity of evacuation routes connecting different tsunami evacuation spaces, and strengthening evacuation spaces with dual-design for emergency and everyday lives.

Specifically, this thesis design project re-evaluates and re-imagines tsunami bōsai evacuation spaces of coastal towns in the southern tip of the Izu Peninsula region. The region has been identified as highly vulnerable to tsunamis propagated by the Nankai Trough. The project critically interrogates current typologies of existing evacuation towers and public spaces operating solely for emergency uses. Instead, it proposes an evacuation space that actively engages with the ecological environment and local communities to support coastal livelihood and economy on a daily basis on top of providing safer high ground and routes to evacuate during a tsunami. This thesis firmly believes that designing tsunami evacuation space should simultaneously involve care, nurture, and support for coastal landscape and society. Furthermore, evacuation spaces and buildings for coastal communities in Japan should be designed accessible to the elderly and facilitate elderly care who make up the sociodemographic of coastal inhabitants, facilitating the needs of those most vulnerable to disasters.