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These tunnels stop part of Tokyo flooding

Tom Scott | November 20, 2025



If you believe the hype, then the Metropolitan Area Underground Discharge Channel stops Tokyo flooding. It doesn’t. But it is one colossal part of a huge network of flood defences that protect a city that would otherwise be… well, very wet.

MORE ABOUT THE DISCHARGE CHANNEL:

The Discharge Channel’s site (in Japanese): http://www.ktr.mlit.go.jp/edogawa/gaikaku/

Advice for English-speaking visitors:
https://matcha-jp.com/en/4002

REFERENCES:

“Below sea level” and “aging levees”: http://www.kensetsu.metro.tokyo.jp/content/000028631.pdf [PDF, parts translated in https://www.nytimes.com/2017/10/06/climate/tokyo-floods.html ]
“All that protects the two and a half million people”: https://mainichi.jp/english/articles/20180823/p2a/00m/0na/007000c
Discharge channel stats: http://www.japanriver.or.jp/EnglishDocument/DB/file/004%20Kanto%2079(T.O-12).pdf [PDF]

THANKS TO:
Local fixer: Yamada Masato
Post translator: Dominic Jacobs

Edited by Michelle Martin (@mrsmmartin)

I’m at http://tomscott.com
on Twitter at http://twitter.com/tomscott
on Facebook at http://facebook.com/tomscott
and on Instagram as tomscottgo

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Written by Tom Scott

Comments

This post currently has 45 comments.

  3. @carneriansimon6652

    November 20, 2025 at 12:10 pm

    This is the largest, but not the only one. There are similar systems in place in other cities in Japan, and some are currently under construction. Construction will be carried out if necessary, even if there is no recession. Let's find out more.

  4. @paulb2092

    November 20, 2025 at 12:10 pm

    Rain is not more intense and frequent than in previous decades in Tokyo. The whole purpose of this is to avoid the drastic flood damage of previous decades.

  11. @CoMorbiditty

    November 20, 2025 at 12:10 pm

    Sad to say there arent governments prepared to spend money on its people. But that holding tank is terrifying. Anything like that and dams just terrify me for some reason

  15. @Sergeantmajormario

    November 20, 2025 at 12:10 pm

    Imagine you're an engineer in one of Japan's greatest defences, you hear that some English guy is gonna come down and do a bit to camera about your work and you don't think much of it, even as you can hear the faint chatter.

    Then randomly you hear silence followed by "ECHO!" being bounced your way

  37. @TheHonestPeanut

    November 20, 2025 at 12:10 pm

    Imagine what an amazing civilization we'd have if governments spent the majority of their money on people, infrastructure and science instead of militaries, bribes and blatantly stealing it for the already rich.

Comments are closed.

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