Water level meter data of Chikuma River Missing before 4:00 am Breaking around this time or Oct. 16 19:49
The data of the water level meter installed near the embankment downstream of the Chikuma River near the place where the embankment broke was found to be the last missing data before 4 am on the 13th. The water level gauge seems to have been washed away, and the Ministry of Land, Infrastructure, Transport and Tourism considers that there may have been a breach at this time and decides to investigate in detail.
This water level meter is a simple water level meter installed by the Ministry of Land, Infrastructure, Transport and Tourism in order to use it for disaster countermeasures such as floods, and is called a “crisis management type water level meter”.
It was installed near the embankment in the Hoho area, Nagano City, several hundred meters away from the place where the embankment broke down on the Chikuma River.
According to the remaining water level data, the water level reached about 3 meters to the highest point of the dike at 9:45 pm on the 12th.
After that, the water level rose and it reached 1 meter until the highest point of the levee at 11:00 pm. It reached the height of the levee at 0:20 am on the 13th and the water overflow seems to have started.
And at 3:50 am, at the end of observing a water level 73 centimeters above the height of the embankment, we found that the data was missing.
It seems that the water level gauge was washed away at this time.
The Ministry of Land, Infrastructure, Transport and Tourism confirmed the breakdown at 5:30 am on the 13th and announced “Failure” at 6:00 am. However, around 4 am before the water level data was lost, I think there is a possibility that the levee was broken.
In the future, the Ministry of Land, Infrastructure, Transport and Tourism will investigate the detailed time and situation of the levee breakage based on the situation of the levee and the testimony of residents.