Chikuma River Embankment Confirmed several damages Expert "Possibility of spreading expansion" October 15 18:26
Experts surveyed the site of Hobo, Nagano City, where the Chikuma River embankment broke down due to the record heavy rain of Typhoon No. 19, and as a result, there were confirmed several locations where the embankment was partially broken even near the place where it broke. It was. The expert said, “There was a possibility that the scope of the rupture was further widened. We do not have to overtrust the embankment and we need to think about how to respond in the event of an emergency.”
The survey was conducted by Professor Junichi Yoshitani of Shinshu University's Faculty of Engineering, who specializes in river disaster prevention and is well-versed in the Chikuma River. .
Prof. Yoshitani analyzed the cause of the breach, analyzing that the river water overflowing beyond the dike was scraping the soil on the side of the residential area of the dike, and the dike gradually collapsed.
In addition, in the range of several hundred meters upstream of the breached place, Prof. Yoshitani confirmed that there were several places where the soil on the side of the embankment's residential area had been greatly shaved. But it was n’t funny, and there was a possibility that the scope of the breakdown was even wider. ”
On the 12th of this month when this typhoon was approaching, in Nagano Prefecture, we recorded the largest amount of rain in the history of observation in Kitaaigi Village and Saku City.
Prof. Yoshitani points out that countermeasures that do not rely solely on embankments are indispensable as natural disasters are expected to increase due to global warming, such as the occurrence of a huge typhoon.
Prof. Yoshitani said, “Up until now, we have been able to prevent disasters by building a dike in the Chikuma River, but it is important to recognize that it is not possible to prevent it alone. It ’s getting more and more important. ”