ダムあれば被害抑制の可能性　球磨川流量３分の２に―国試算

　熊本県を襲った７月の豪雨で氾濫した球磨川水系について、国土交通省九州地方整備局は２５日、建設計画が中止された「川辺川ダム」が整備されていた場合、人吉市ではピーク時流量を約３分の２に低減できたなどとする試算を公表した。熊本県庁で同日あった国、県、流域１２市町村でつくる検証委員会の初会合で報告した。浸水被害を抑えられた可能性があるとみている。
　九州地方整備局によると、人吉市内の水位観測所周辺の浸水高などから推定されるピーク時の球磨川の流量は毎秒約７５００トン（速報値）。川辺川ダムで洪水調整できた場合、毎秒約４７００トンまで減らせたとみており、次回の検証委で想定浸水域を示す予定。（2020/08/25-20:23）

A scrapped dam project could have limited the damage from the flooding of the Kuma River system in the heavy rains that hit the southwestern Japan prefecture of Kumamoto in July if the dam had been built, government calculations have shown.
   The estimations showed that the dam, called the Kawabegawa dam, may have reduced the peak river flow rate to two-thirds in the city of Hitoyoshi in Kumamoto if it had been constructed as planned.
   The calculations were compiled by the land ministry's Kyushu Regional Development Bureau and announced at the first meeting of a disaster review committee made up of members from the central government, the Kumamoto prefectural government and 12 municipalities located alongside the river system on Tuesday.
   According to the bureau, the peak flow rate of the Kuma River at the time of the disaster, which led to many lost lives and homes, is estimated to have come to around 7,500 tons per second on a preliminary basis, based on the flood levels around the water level observation stations in Hitoyoshi.
   If flood adjustment was done through the dam, the bureau estimates that the peak flow rate would have fallen to around 4,700 tons per second.