In September 2008, Kumamoto Governor Ikuo Kabashima called for the existing Kawabegawa Dam plan to be withdrawn, and in September 2009, Land, Infrastructure, Transport and Tourism Minister Seiji Maehara of the Democratic Party-led Hatoyama administration announced that the project would be cancelled.
Before an effective alternative to dam-based flood control had been completed, the Kuma River basin was devastated by the July 2020 heavy rain disaster.
This article questions the responsibility of political leaders, flood-control policy, and the electorate.

August 4, 2020
The Cancellation of the Kawabegawa Dam and the July 2020 Heavy Rain Disaster—Questioning the Responsibility of the Kabashima Administration, the Democratic Party Government, and Flood-Control Policy for the Kuma River
【Background】
Record-breaking rainfall struck southern Kumamoto Prefecture between July 3 and 4, 2020.
Large-scale flooding occurred throughout the Kuma River basin, causing devastating loss of life and property in Hitoyoshi City, Yatsushiro City, Kuma Village, and other communities.
Among the worst-hit facilities was the Senjuen nursing home in Kuma Village.
According to records compiled by Japan’s Ministry of Land, Infrastructure, Transport and Tourism, approximately 1,020 hectares were inundated along the Kuma River, affecting about 6,110 homes.
The final figures later compiled by Kumamoto Prefecture recorded 65 deaths and two people missing in the prefecture.
The figures of 51 deaths and 11 missing persons quoted below were preliminary figures available when the source article was written.
In 1966, the national government announced a plan to construct the Kawabegawa Dam on a tributary of the Kuma River, primarily for flood-control purposes.
After decades of opposition, Kumamoto Governor Ikuo Kabashima declared in September 2008 that the existing dam plan should be withdrawn and that flood-control measures not dependent on a dam should be pursued.
In September 2009, Seiji Maehara, Minister of Land, Infrastructure, Transport and Tourism in the Democratic Party-led government of Prime Minister Yukio Hatoyama, announced the cancellation of the project.
The national government, Kumamoto Prefecture, and the municipalities in the river basin subsequently considered alternatives, including river-channel excavation, higher levees, and flood-retarding basins.
However, before a fundamental alternative flood-control system had been completed, the basin was struck by the catastrophic rainfall of July 2020.
The following passage comes from an article published on the blog of a reader of this column.
It contained facts that were new even to me.
They were probably also unfamiliar to many other readers.
It was an extremely informative and thought-provoking essay.
【Quotation】
During the heavy rainfall then affecting southern Kumamoto, the Kuma River, commonly described as a “raging river,” overflowed at 11 locations, while a levee failed at one location.
In Kuma Village, where the Senjuen nursing home suffered a large number of casualties, and in Hitoyoshi City and other communities along the river, preliminary reports at the time recorded 51 deaths, 11 people missing, and approximately 6,100 flooded homes.
The human and material losses were expected to increase further.
The Kuma River suffered major floods for three consecutive years from 1963 through 1965.
In July 1965, a stationary seasonal rain front brought continuous heavy rainfall and caused the largest flood of Japan’s postwar period in the basin.
Large parts of central Hitoyoshi were inundated, and a levee also failed in Yatsushiro.
Reports stated that 1,281 homes in the basin were damaged or washed away and that more than 10,000 homes were flooded.
In July 1966, the national government announced a plan to construct the Kawabegawa Dam, one of the largest dams of its kind in Kyushu, on a tributary of the Kuma River for flood-control purposes.
Approximately 500 households were relocated from Itsuki Village, which was to be partly submerged by the reservoir.
Opposition to the project nevertheless spread among local residents and political leaders.
In September 2008, Kumamoto Governor Ikuo Kabashima declared that the existing project should be withdrawn and opposed its continuation.
In September 2009, the Democratic Party-led government of Prime Minister Yukio Hatoyama took office.
Under Seiji Maehara, who became Minister of Land, Infrastructure, Transport and Tourism, and Kiyomi Tsujimoto, who became a senior vice minister, the government announced the cancellation of the Kawabegawa and Yamba dam projects.
Maehara appeared so delighted and carried away by the change in government that he announced the cancellation of both projects with evident excitement.
The national government, Kumamoto Prefecture, and the 12 municipalities in the river basin then discussed alternatives to the Kawabegawa Dam.
Plans combining river excavation, higher levees, and flood-retarding basins were considered.
However, their estimated costs reportedly ranged from ¥280 billion to ¥1.2 trillion, while construction was projected to require between 45 and 200 years.
Despite the devastation caused by the 2020 flooding of the Kuma River, Governor Kabashima emphasized on July 5 that the decision to cancel the Kawabegawa Dam reflected the wishes of the people of Kumamoto and that his opposition had not changed.
He said that he was deeply shocked by the scale of the damage.
He also stated, in substance:
“We have pursued flood control without relying on a dam, but it could not be implemented because of the enormous cost.”
“We will examine flood-control measures not dependent on a dam to the fullest possible extent.”
“We have been given another opportunity to consider them.”
To the writer of the source article, these remarks sounded as though the governor were speaking about someone else’s responsibility.
Before entering politics, Kabashima had been a professor at the University of Tokyo.
He was first elected governor in 2008 and won a fourth term in 2020, entering his thirteenth year in office.
Yet, in the source writer’s view, nothing had changed and no meaningful progress had been made.
The writer harshly described him as a typical example of an academic unable to deal with practical reality.
In a democracy, the members of the National Diet, prefectural and municipal assemblies, governors, and mayors are chosen by the people.
Whether the outcome is good or bad, the voters who elected them also bear responsibility.
Their choices eventually return to them like a boomerang.
This disaster should not simply be dismissed as a natural calamity.
The responsibility of political leaders and government authorities who opposed the dam but failed to complete an effective alternative must also be examined.
In that sense, the source writer argued that the disaster also had a man-made dimension.
Construction of the Yamba Dam in Gunma Prefecture was also temporarily suspended after Minister Maehara announced its cancellation under the Democratic Party government.
The government of Prime Minister Yoshihiko Noda later decided to resume construction, and the project was completed after the Liberal Democratic Party returned to power.
During Typhoon Hagibis in October 2019, while the reservoir was still undergoing trial impoundment, the Yamba Dam stored a vast volume of floodwater.
Subsequent research estimated that the upper Tone River dam system reduced the water level at the Yattajima monitoring point and that the Yamba Dam alone accounted for a maximum reduction of approximately 0.6 metres.
【End of Quotation】
【Factual Note】
The Yamba Dam is located on the Agatsuma River in the Tone River system.
It is therefore inaccurate to state directly that the dam prevented the Arakawa or Sumida River from flooding.
What has been demonstrated is its flood-control effect within the Tone River system.
Research has estimated that the Yamba Dam alone reduced the water level at Yattajima in the upper Tone River by as much as approximately 0.6 metres.
The Iwabuchi Floodgate, rather than the Yamba Dam, controls the inflow of floodwater from the Arakawa into the Sumida River.
Official records also confirm that Governor Kabashima called for the existing Kawabegawa Dam plan to be withdrawn in September 2008 and that Minister Maehara announced the project’s cancellation in September 2009.
After the July 2020 disaster, however, Kabashima changed his previous position.
In November 2020, he called on the national government to construct a new flood-control-only dam as part of what he described as “green basin flood control.”
【Conclusion】
Flood-control policy cannot be reduced to a simplistic choice between building a dam and building no dam at all.
Those who oppose a dam must complete an alternative capable of providing equal or greater protection within the time available.
River-channel excavation, stronger levees, flood-retarding basins, forest management, and evacuation systems may all form part of a comprehensive policy.
However, plans that exist only on paper cannot save lives.
Approximately 11 years passed between the withdrawal of the existing Kawabegawa Dam plan in 2008, the national government’s cancellation announcement in 2009, and the July 2020 disaster.
How much of the proposed flood-control system not dependent on a dam was actually completed during that period?
Why was a fundamental alternative not put in place?
Who bears responsibility for that delay?
Political leaders and public authorities must be held accountable.
The electorate that chose those leaders and supported their policies also has a duty to examine the consequences.
Repeating that a disaster was “beyond expectations” after people have died will not prevent the next tragedy.
Flood-control policy that protects human life requires more than ideals and slogans.
It requires facilities and measures that actually function—and that are completed before disaster strikes.