“Is Backwater Occurred?” Ibaraki Flooding at the Nakagawa Junction Point Oct. 17 15:55
A river expert at the University of Tsukuba conducts a survey of the floods in Ibaraki Prefecture, and in Mito City, the water level of the Naka River has risen, so the water in the tributary that joins is blocked and the water level rises. I pointed out that it seems to have occurred.
The field survey was conducted by Naoki Shirakawa, an associate professor at the University of Tsukuba, specializing in river engineering.
Associate professor Shirakawa conducted a survey at the point where the Fujii River, a tributary of Iitotocho in Mito City, merged with the Naka River, and the grass left behind in the Fujii River basin was caught on the guard rails against the water flow. I confirmed that.
As this indicates that the river flowed in the reverse direction, the water level of the Nakai River rose due to heavy rain, and the water level of the Fujii River was blocked and the water level rose while flowing back, a phenomenon called backwater occurred I am analyzing that it may be.
Also, at the place where the Kuji River embankment flowing through Tomioka, Hitachi-Omiya City broke down for about 100 meters, water that exceeded expectations flowed into the river, and when it overflowed from the embankment, the embankment was eroded little by little and led to failure I am not sure.
Associate professor Shirakawa said, “There is a limit to the cost of building a dike. In reality, it is difficult to hold down the flow of water only in a river in the event of an unexpected heavy rain disaster. It is necessary to take measures for flood control, such as developing a reservoir based on the premise. "