Tokyo’s massive flood protection facility might not be “enough” due to climate change

By Elisa Jiménez Alonso

In Tokyo, an enormous underground flood protection system pumps excess water out of the metropolitan area into the sea and has reduced flood occurrences massively. But, climate change might take it to its limits.

When you look at a photograph of the Metropolitan Area Outer Underground Discharge Channel, or G-Cans, you might be reminded of J.R.R. Tolkien’s Mines of Moria and the terrifying Balrog that lived there. However, it is the world’s largest underground flood water diversion infrastructure, built on the outskirts of Tokyo.

The numbers associated with this cavernous super structure are truly impressive: 50 metres beneath the surface, five containment silos, each 65 metres high and with a diameter of 32 metres, are connected by a 6.3-kilometre network of tunnels. The silos are so big, they could fit the Statue of Liberty inside. The structure also has a large cistern, the “Underground Temple”, 18 metres high, 78 metres wide, and 177 metres long with 59 massive pillars and connected to the drainage facility of the system which consists of 4 pumps that can pump a total of 200 cubic metres of water per second.

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