On the 8th, the prefectural investigative committee investigating the cause of the debris flow that occurred in Atami City, Shizuoka Prefecture, compiled a final report, saying, ``Inappropriate embankments with insufficient drainage measures were created where groundwater flows into, and heavy rains caused further damage. The infiltration of groundwater caused the debris flow.”
Due to the large-scale debris flow disaster that occurred in Atami City in July last year, Shizuoka Prefecture set up a verification committee to investigate the cause, and compiled the final report on the 8th.
According to that, based on the analysis results that reproduced the collapse of the embankment, the place where the debris flow started was that groundwater was flowing from the Narusawa River basin on the mountain side, and there was insufficient solidity and drainage measures. He points out that the 50-meter-high inappropriate embankment was created, which made it easy to absorb water at all times.
Then, due to the heavy rain that started two days before the debris flow, the groundwater infiltrated further, causing the groundwater to rise from the bottom to the top of the embankment, causing a "water absorption softening phenomenon" in which the soil suddenly became muddy. .
For this reason, the soil collapsed one after another from the bottom at three places in the embankment, and it was concluded that "resulting in the collapse of almost the entire embankment."
In response to the final report, Director Namba of Shizuoka Prefecture said, "We will publish the report nationwide so that debris flows like this will never be repeated nationwide, and will be useful in the prefecture's response going forward." rice field.