Connecting Delta Cities

Tokyo

Tokyo: Trends

Trends: socio-economic, climate change

Japan has the second highest GDP in the world. In 1940 the metropolitan area of Tokyo counted 7.4 million inhabitants; this figure has increased to 12.8 million inhabitants in 2008 (about 10% of Japan’s total population). Tokyo has a high economic value and a very well-developed network of infrastructure. Its subway sJapan has the second highest GDP in the world. In 1940 the metropolitan area of Tokyo counted 7.4 million inhabitants; this figure has increased to 12.8 million inhabitants in 2008 (about 10% of Japan’s total population). Tokyo has a high economic value and a very well-developed network of infrastructure. Its subway system is very dense and the city has a high concentration of underground shopping malls. Dike failure would lead to a disastrous flooding of these underground areas. A simulation has shown that if an Arakawa dike near Kitasenju in Adachi Ward would breach, water would flow into the subway at Kitasenju station and reach Otemachi station in only two hours.

In response to the growing demand for housing in Tokyo Metropolis the residential areas are expanding towards the less elevated western region and the flood prone eastern area. The original inhabitants of flatland areas knew for many generations which areas the rivers would flood the hinterland during extreme discharges and where it was relatively safe to live in. Damage caused by inundation to the newly build houses in these areas is not compensated by the Japanese government. Still, flood prone land is cheap so many new houses are built in these areas. Only a few of these houses were adjusted in such a way that the ground floor could be flooded without too much damage.

Climate change projections for Japan show that temperatures are rising and that the winter and summer precipitation are likely to increase. Additionally, an increase in the frequency of intense precipitation events in East Asia is very likely. The sea level is expected to rise by 0.35 m towards the end of the century.

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