小名木川かさ上げ護岸の歴史

There was a big explanation board and it was like below. The Onagi River is a canal that was opened and excavated around 1590 at the order of Ieyasu Tokugawa by Shirobe Onagi. In the Edo period, it was a river that carried Gyotoku salt, suburbs of agricultural products, rice from the Tohoku region, soy sauce, etc. into the city of Edo, and was also called the "Salt Road." The area where the Onagi River flows is originally a lowland because it developed as an urban area of ​​Edo by reclaiming the turbulent Arakawa River (currently the Sumida River) and the delta deposits at the mouth of the Tone River. I have been damaged. Furthermore, ground subsidence progressed due to excessive pumping of groundwater accompanying the development of the industrial zone from the end of the Meiji era, and the Koto Triangle surrounded by the Arakawa and Sumida rivers was below the high water level of Tokyo Bay and is a zero meter zone. It is also called. In order to protect the town with continued subsidence from flood damage, the revetment of the Koto internal rivers (collectively the rivers that flow through the Koto Triangle), including the Onagi River, had to be raised. However, due to repeated raisings as a first-aid measure, the seawall and rivers have been divided and structurally weakened, and there has been concern over the risk of flood damage due to the collapse of the seawall in the event of a large earthquake. In order to protect the area from this earthquake and flood, Tokyo began a river development project for the Koto inner river in 1969. The deadline was “Measurement of water level reduction” to keep the water level below normal level in March 1993. At the Onagi River, we are cutting off the upper part of the "bulb up revetment" that has become unnecessary due to the drop in the water level, and are working on the construction of a masonry wind revetment that recreates the Edo mood as a "salt road" is being regenerated. This old revetment of the Onagi River conveys the history of the "Kasage Revetment" that has protected the area from flood damage to future generations as the "Road of Salt" is regenerated, and keeps the people living in the lowlands aware of flood control. In order to do so, we will save a part of it.