Uchikura & Co., LLC

How Does Tokyo Deal with Flooding?

Tokyo is one of the largest and most densely populated cities in the world. When typhoons and heavy rain hit the city, where does all that water go?

 

One answer is underground.

 

Beneath Tokyo’s Ring Road No. 7 lies the Kanda River–Ring Road No. 7 Underground Regulating Reservoir, a massive flood-control tunnel built about 40 meters below ground.

 

The tunnel stretches approximately 4.5 kilometers and can temporarily store about 540,000 cubic meters of floodwater. During extremely heavy rainfall, when rivers such as the Kanda River rise to dangerous levels, excess water is diverted into this underground reservoir.

 

Instead of allowing the rivers to overflow into surrounding neighborhoods, Tokyo temporarily stores the water beneath the city. After the storm passes and river levels fall, the stored water can be safely released.

 

What I find fascinating is that most people driving along Ring Road No. 7 probably have no idea that such a huge structure exists beneath them.

 

Tokyo cannot stop typhoons or heavy rain. Instead, it has learned how to manage the water.

 

Sometimes the most important infrastructure is the infrastructure we never see.