Tokyo, the vast capital city of Japan, was first called Edo – or ‘estuary’, a reference to the twin Tama and Sumida Rivers that flow into the estuary of Tokyo Bay. The global city of Tokyo, like Shanghai, is in one of the most densely populated regions on earth with the greater Tokyo metropolitan area estimated to exceed 35 million people.


The Tokyo region is located in a geological fault zone, and is thus subject to earthquakes and Tsunamis. The Tokyo metropolis is built on the large flood plain of the Tama and Sumida Rivers, along with the Edo and Ara Rivers, hence a system of dikes and levees is required to protect low-lying areas of the city. Tokyo has a subtropical climate, and is subject to heavy precipitation in June and July, when the risk of flash floods is highest.

Heatwaves have recently become more frequent in Tokyo, and are exacerbated by the ‘urban heat island’ effect in the city, especially at night. Typhoons have also become more extreme (especially in 2004), and there is concern that the high sea surges caused by typhoons will threaten the city, especially if combined with a rise in global sea levels. In 2007 the Tokyo Metropolitan Government released its Tokyo Climate Change Strategy, a 10 year project that aims to reduce 2000 greenhouse gas emissions by 25% by 2020.

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Tokyo projects

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