An underground archeological site that protects the Tokyo Metropolitan Area and Tokyo. Explore the Metropolitan Area Outer Discharge Channel!

This time I visited the Metropolitan Area Outer Discharge Channel and would like to introduce it to you. The Metropolitan Area Outer Discharge Channel is a large-scale flood control facility for the surrounding areas of Tokyo, Saitama, and Chiba Prefectures. The project is designed to prevent from flooding and especially to reduce flood damage caused by heavy rains in central Tokyo. Advance reservations are required for the tour. Please make reservations through the official website.

見学会への参加注意事項 | 首都圏外郭放水路

地域の治水施設である「首都圏外郭放水路」の役割をもっと深く知っていただけるように、社会実験第２弾として新たな3コースの見学会がスタート。首都圏外郭放水路の壮大さをぜひご体感ください。

gaikaku.jp

(Tour fee: from 1,000 JPY) As of October 2024

Main Features

At the beginning of the tour, there is an explanation through panels about the Metropolitan Area Outer Discharge. You can see at a glance how the facility was built and its structure. After the explanation, you will actually visit the site, which will help you understand it better.

Below is a brief introduction to this site as well.

1. Structure:
   • The system consists of an underground tunnel and a reservoir, and is designed to efficiently discharge rainwater.
   • The tunnels are approximately 6.3 kilometers long, with some sections approximately 10 meters in diameter.
2. Functions:.
   • During heavy rainfall, incoming rainwater is temporarily stored, treated in underground reservoirs, and then gradually drained.
   • This prevents the river level from rising and reduces the risk of flooding in the surrounding area.
3. Operation:.
   • An automatic control system is in place to respond quickly according to rainfall.
4. Environmental Considerations: The facility is surrounded by green areas.
   • The facility is surrounded by green areas to protect the local environment.

The Metropolitan Area Outer Discharge Channel plays an important role not only in flood control, but also in disaster prevention in the region, and plays an important role in protecting the safety of many people.

There are approximately 59 columns totaling 25 meters in height. These pillars support the ceiling of the reservoir. The reservoir covers an area of approximately 40,000 square meters and has a maximum storage capacity of approximately 600,000 cubic meters. This vast space serves to efficiently store rainwater during heavy rains. The overwhelming space will surely take your breath away.

It is said that bulldozers, dump trucks, and other heavy equipment are lowered from the ground through this hole when removing the mud that has accumulated in this canal. Believe it or not, you can see the construction several times a year, so if you are interested, please inquire. They can tell you the dates.

The Metropolitan Area Outer Discharge Channel seen from the ground. Heavy machinery is said to be unloaded from this covered area. At a glance, it is not obvious from the ground. This is truly a behind-the-scenes powerhouse of the Tokyo metropolitan area, including the Tokyo Metropolitan Government.

How was it?

We have introduced some fairly minor places, but since they are only about an hour away from central Tokyo, we encourage you to visit them. If you go to a sightseeing spot that is different from the others, you will definitely be the talk of the town when you return to your home country! It is also a good way to learn about society, so we recommend it to those who want to do something different!