On May 23, 2026, we traveled to Kasukabe City to make a research visit to the Metropolitan Area Outer Underground Discharge Channel, which in Japanese is Shutoken Gaikaku Housuir (首都圏外郭放水路). The nickname of this place is Chika Shinden (地下神殿) which means ‘Underground Parthenon.’
This ‘Underground Parthenon’ is a facility designed to prevent flooding in a river basin. This basin is located nearby by three large rivers and houses five small rivers inside the basin. The rivers in the basin are prone to flooding. Each of these five rivers are interconnected via a man-made underground tunnel system. If the water level exceeds a certain point in those five rivers, the overflow is carried away via those tunnels and is stored in one large underground chamber near Edogawa River. Later the water in the chamber is pumped out to that river which can handle large amounts of water.
The facility construction started in 1993 when the Japanese bubble-economy still had some effect. The total construction cost was 230,000,000 yen This is a genuine public project which means it was funded by the public. Additionally, in order to financially support facility management, a private entity manages tourism for this location. A designated system (Shitei Kanrishya Seido指定管理制度) has been adopted for this tourism management. This is a great example of public private partnership (PPP) in action.
We really were fascinated by how such impressive Japanese civil engineering can be used in two ways: for flood management and for tourism. Without PPP, no revenue would be possible.
The ‘Underground Parthenon’
Professor Noriko and Students (1 student from the JICA program and 3 international students) standing under the huge pump.
A popular Japanese character, Kureyon Shin-chan, helps promote the Metropolitan Area Outer Underground Discharge Channel.
Official Website (首都圏外郭放水路): https://gaikaku.jp