[From July Issue 2010]

In the underground of Kasukabe City, Saitama Prefecture, there is a vast space that looks like a gigantic shrine-like structure, where 59 pillars, each 2 meters wide and 18 meters high, occupy a space 78 meters wide by 177 meters deep. This is all located 22 meters below ground level, and resembles the Parthenon, but at the center of the earth. SUZUKI Momoko, one observation-tour participant said, “I was overwhelmed by the gigantic pillars. At that depth, the earth was quiet and mystic.”

This “shrine” is actually part of a 6.3 kilometer drainage canal, built to help prevent floods in the Nakagawa River basin. Its construction started in 1993 and was completed in June, 2006. It started to partially operate in 2002.

The free Metropolitan Area Outer Underground Discharge Channel observation-tours are open to the public just by making an application via the Internet, by phone, or directly at the information desk. Each tour takes about one and a half hours, three times a day, from Tuesday through Friday. Since the number of participants per tour is limited to only 25, they are usually fully booked soon after they are offered. Accompanied by a PR person, participants visit three places: Ryu-Q-kan, the roof of administrative building, and the pressure-controlled water tank (where water is held).

Ryu-Q-kan is a museum that showcases the facility’s system, as well as offering various, other flood-prevention information. Using models and maps, their explanations are well-reputed to be easily understandable. From the roof of the administrative building, participants can observe the flow and the water level of the Edo River. The supporting Parthenon-like pillars of the pressure-controlled tank are especially popular with the people on the tour. When it floods, excess water fills the tank hiding the pillars from view.

The five vertical, water-intake shafts resembling giant wells, like giant wells connect directly to the underground tunnel. Each shaft is 70 meters deep and 30 meters wide, enabling it to swallow the entirety of New York’s Statue of Liberty. Unfortunately, for safety reasons the tunnel and the vertical shafts are off limits during the tour.

The low-lying characteristics of the land in the Nakagawa basin make it easy for water to accumulate, causing both flooding and inundation damage. As a result, this system of diverting water from the small, flood-prone river to a bigger river was conceived.

The majority of people who join the observation-tour come from the Kanto Area, with the number of men slightly exceeding that of women. Participants say that, “It was interesting to see a place where we usually can not go” and that “we appreciate that we can live safely because of the facility.” ARAKI Shigeru, who is in charge of the facility, says: “I would like to have many people learn about the Metropolitan Area Outer Underground Discharge Channel, and make them more aware of disaster prevention.”

Edogawa River Office, Metropolitan Area Outer Underground Discharge Channel

Text: MUKAI Natsuko









江戸川河川事務所 首都圏外郭放水路


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