How Japan Keeps Millions of Residents Safe From Floods

The video discusses the world's largest underground water facility located near Tokyo. This facility, known as the Metropolitan Area Outer Underground Discharge Channel, is a massive tunnel system designed to prevent flooding in the region. It features large vertical shafts that store floodwaters and redirect them to a river capable of handling the excess water, thus protecting over 9 million residents from flooding.

How does the Outer Underground Discharge Channel help the residents of the area?

What is the length of the tunnel in the Outer Underground Discharge Channel?