Official
Chuo-ku, protected from typhoon flood damage
Typhoon No. 19 caused flooding of rivers throughout the country. It is not a past form yet, and many people seem to be waiting for relief even as of the 15th. I would like to express my heartfelt sympathy to all those who have been affected.
Chuo-ku and the Toto area have been suffering from repeated floods, but thanks to the multi-layered flood control equipment and the efforts of people involved in flood control, this time it was almost intact in terms of flood damage. With great appreciation, I would like to introduce some of the flood control facilities that have protected us.
If Arakawa was flooded
First of all, take a look at the video saying "It might have been like this."
This video shows Kanto Regional Development Bureau, Ministry of Land, Infrastructure, Transport and Tourism: It is called "Fiction Documentary" Arakawa Flood "H29.3 Revised Edition" produced by Arakawa Lower River Office. Upstream of Arakawa due to typhoon: This is a live-action simulation when the Arakawa floods around the railway bridge on the Keihin Tohoku Line, just a little upstream than the Iwabuchi sluice gate (*) due to heavy rain falling around Chichibu. It depicts the terrible result that office districts such as Chuo-ku and Chiyoda-ku lose all functions. 。 。
※The current Sumida River branches off from Arakawa at the Iwabuchi Suimon (Kita-ku, Tokyo).
Chuo-ku, which is protected by multiple layers
Arakawa has been suffering from floods since ancient times, as the name "Araburu River" is said to be the origin of its name. Conversely, flood control in the eastern capital has a long history that began with the Tonegawa Togen during the Edo period.
Among them, I would like to introduce some of the facilities that protected the Sumida River below. It is a very simple introduction, so if you are interested, please refer to the link.
（１） Arakawa Floodway (now Arakawa)
As you know, in the past, the Sumida River was directly connected to the upper Arakawa River. The rain that fell upstream of Chichibu flowed into the Sumida River as it was. Thanks to the Arakawa Floodway, which was completed by a large construction that took 17 years from 1913, and the Iwabuchi Sluice Gate, which controls it, most of the water flowing through Arakawa is not the Sumida River, It began to flow toward the spillway.
Transition of Arakawa Floodway (Arakawa Lower River Office)
（２） Chichibu 4 Dam
The upstream of Arakawa is the mountains of Chichibu, but there are a number of dams here. The Urayama Dam, Nise Dam, Takizawa Dam, and Kakkaku Dam are called Chichibu 4 Dams. Above all, the combined water storage capacity of both Urayama and Takizawa dams, which started operation in Heisei, is more than 100 million m3!
Even in the huge underground of the Metropolitan Area Outer Floodway (which also prevented the flooding of Nakagawa and other small and medium-sized rivers), which is famous as an underground temple, the water storage capacity is 670,000 m3 (that is a tremendous amount), so the Chichibu dam's dependability is endless!
Arakawa Dam General Management Office
Full operation of underground temple for the first time in four years (Asahi Shimbun)
（３） Arakawa Daiichi Reservoir, Lake Aya
Lake Aya started operation for the first time in 20 years due to this typhoon. Lake Aya has a storage capacity of 10.6 million m3. There is a total of 39 million m3 in the entire Daiichi Reservoir. Currently, the 2nd to 5th reservoirs are under construction and planned. This is also a very reliable ally.
Reservoir (Arakawa Upper River Office)
Facilities for the entire Arakawa River (Arakawa Upper River Office)
（４） Sluice gates along the Sumida River
There are many sluice gates in Chuo-ku, Koto-ku, etc., and are managed by the Tokyo Port and Harbor Bureau and the Koto Flood Control Office. According to the work of the sluice gates, it may be "protecting people from the Sumida River" rather than "protecting the Sumida River", but anyway, on the day of the typhoon, these sluice gates were closed one after another and firmly protected He solidified it.
Sluice gate “Closed Information” (from the e-mail magazine of Koto Flood Control Office)
As of 14:09 on October 12 due to Typhoon No. 19, the following five sluice gates have been closed.
Shin Onagi River Sluice Gate, Tate River Sluice Gate, Oshimakawa Sluice Gate, Sumiyoshi Sluice Gate, Tsukishima River Sluice Gate.
As of 15:00 on October 12 due to Typhoon No. 19, the following five sluice gates have been closed.
Kamihirai Suimon, Imai Suimon, Shinkawahigashi Suimon, Gen Morikawa Suimon, Uchikawa Suimon
I've kept it for you
Chuo-ku was protected by the multi-layered facilities of the Sumida River and Arakawa River, and the efforts of the people involved in it. But where did "rain that fell in the city center including Chuo-ku" go?
The answer is a sewage treatment plant (currently renamed the Water Reclamation Center).
There are two methods for sewage treatment: "merging type" and "split type". The confluence type treats rainwater from sewage (domestic wastewater including toilets) without distinguishing it, and the diversion type is a method of treating rainwater and sewage separately.
Unfortunately, the sewage treatment in the city center is a “joining type”, so if the typhoon like this one or the long rains in July this year exceeds the treatment capacity of the water reclamation center, `` Sewage is almost the Sumida River It will be washed away. " Because it is sewage containing not only rainwater but also sewage, it is full of Escherichia coli and smells bad. This summer, the para-triathlon swim competition in Tokyo was canceled.
It seems that there is a dilemma that it is a traditional "merging type" because it is a city where sewage treatment has been applied from an early stage in history, and it has become a "separate type" in areas where sewage treatment has recently been completed . It is said that the construction period of more than 50 years and the cost of more than 10 trillion yen is required to make the city center a diverted system from now on.
It's a very frustrating story. 。 。
Current Status and Issues of Combined Sewer (Tokyo Metropolitan Sewerage Bureau)
The water quality of Odaiba is bad and the swim is stopped. Paratriathlon World Cup (Nikkei Shimbun)
People raising voices (Shigeru Enomoto Minato-ku, Representative: Interview with Gendai Nikkan)
Sewage discharge under the Rainbow Bridge (posted by a member of the Diet above)