yaz

Water supply infrastructure in the Edo period

The area between Nihonbashi and Shimbashi was a wetland with an altitude of about 3m to 4.5m, called "Edo Maejima". There is a theory that the Nihonbashi, Kyobashi, and Ginza areas were reclaimed by Tokugawa shogunate, but landfills have not been carried out in areas where the same height as the current altitude was maintained. Tokugawa shogunate was not a landfill, but originally a wetland but a strong land, so it was chosen to develop it as the center of Japan. According to the Keicho era Edo map (1602, 1602), you can see the sea of Hibiya Inlet, but the 11 Funairi moats between Nihonbashi River and Kyobashi River, which were introduced earlier, have not been dug. It became a candidate site for Funairi moat at the second world contract (from 1611), and was a place to accept stone walls for Edo Castle, which was mainly quarried in the Izu region.

In this blog, I'm talking about it.　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　①　Why was the Funairi moat dug in Edo Maejima?　　　　　　　　　　　　　　　　　　　　　　　　　　　　②　Relationship between the water supply facilities and the stratum of Edo Maejima　　　　　　　　　　　　　I will consider it.

 

Edo Maejima and Edo Castle

Edo Maejima and Edo Castle Water Supply Infrastructure in the Edo period

If you look at the cross section of the stratum on the cut line from Yotsuya to Hatchobori through Edo Castle, it looks like the attached figure. From Yotsuya to Edo Castle, there is a flood plateau at an altitude of about 20m, and after the Hibiya Inlet, Edo Maejima, which is about 3m to 4m above sea level. Unlike the soft stratum made by reclaiming the delta (coast lowland) at the mouth of the Sumida River and Arakawa River, Edo Maejima is a strong stratum called the Tokyo Formation of clay and sand. This Tokyo layer was more than 15m thick and was considered to have had enough strength to accept a stone steel ship carrying stone wall megaliths. Since the water depth of the Nihonbashi River is around 4.1m, it is expected that other Funairi moats have been dug to the same depth. Edo Maejima was selected as a candidate site for excavation of Funairi moat, which transports it by stone steel boat and accepts it because of the geographical proximity to create the stone wall of Edo Castle and secures a solid stratum. I guess.

This is why a commercial area called Nihonbashi Ginza was developed on Edo Maejima.

A commercial area called Nihonbashi Ginza was developed on Edo Maejima. Water infrastructure in the Edo period

Many factors can be considered that Edo Maejima, including Nihonbashi and Ginza, flourished as a commercial area, but one of them is the laying of waterworks. The first water supply "Kanda Josui" built by Okubo Shusui at the order of Ieyasu Tokugawa was also supplied to Edo Maejima, including the fish market in Nihonbashi. The topography of Edo Maejima is greatly related to the realization of this infrastructure construction.

Let's take a look at the cross section (attached) of "Chuo-dori (Ginza-dori)" which is the ridge of Edo Maejima using package software called "Super Topography". It is divided into Ginza 3-chome to Ginza 6-chome to Ginza 8-chome, and is shown. You can see that the area around Ginza 4-chome and 8-chome is almost at the top.

 

The slope between Chuo-dori and the outer moat is about 3/1,000.

The slope between Chuo-dori and the outer moat is about 3/1,000, Edo period water supply infrastructure

In the early Tokugawa period, Okubo Shusui drew Kanda Josui and laid a water supply facility on Edo Maejima, including the Nihonbashi Fish Bank. It is imagined that a main water supply was laid on the ridge of Edo Maejima and distributed to commercial facilities. Was it possible to distribute natural water?

Looking at the cross section of Edo Maejima on the line connecting the Ginza 4-chome intersection and the outer moat, it looks as shown in the attached figure. When you calculate the gradient, it is as follows.

①　The distance between the outer moat and Ginza 4 intersection or the outer moat and Ginza 8 intersection is about 360m.　　　　　　　　　　　　　　　②　The altitude difference between the outer moat and the intersection of Ginza 4 or Ginza 8 is 90 cm.　　　　　　　　　　　　　　　　　　　　　③　The slope is 0.0028.

It is generally said that the slope of places where water flows, such as modern bathrooms, is 3/1,000, so even in the Edo period, water was naturally released at this slope. It's great.

[References]

①　Tokyo Metropolitan Geological Survey Association Technical Note (Showa 63.7) NO.3

②　Software "Super Topography" (written by Tomohiko Sugimoto)

③　News from Local Room Chuo Ward Kyobashi Library