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A scrapped dam project could have limited the damage from the flooding of the Kuma River system in the heavy rains that hit Kumamoto Prefecture 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.

In the next committee meeting, the bureau plans to indicate the areas that are assumed to have been flooded if the dam had been constructed.

With the dam’s main construction work thwarted by protest movements by locals, leaders of the municipalities around the river system demanded that the project be scrapped.

The central government, then led by the now-defunct Democratic Party of Japan, decided to end the project in 2009 after Kumamoto Gov. Ikuo Kabashima voiced opposition.

Since then, the central and prefectural governments had created a river channel in hopes of controlling floods without building a dam. They drew up 10 other water control ideas, including raising of riverbanks, in November last year.

The central government, however, has not completed legal procedures to officially abolish the dam project.

Following the downpours, the municipalities in the river basin have been urging the central and prefectural governments to implement drastic flood control measures, including dam construction.

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