The combined length of major rivers crisscrossing Japan and classified by the government as "Class A" comes to 88,000 km, or more than twice the circumference of the globe — quite a large figure for this small country.

Since the prehistoric age, these rivers have enriched people's lives, but at the same time snarled at them with floods. The latter fact is still reflected in the names of some of the rivers. For example, the Kinugawa River, which played havoc with large areas north of Tokyo in September, literally means a "river of a demon's wrath," while the Arakawa River in Tokyo denotes a "wild river."

The Japanese people are beginning to forget to regard these rivers with the awe they deserve, and the floods in Tochigi, Ibaraki and Miyagi prefectures last month almost look like deserved punishment.

The most fundamental cause of the flooding is traced to policy mismanagement by the Ministry of Land, Infrastructure, Transport and Tourism, in particular its refusal to deviate from the idea that building dams solves all problems related to rivers. Also responsible have been urban development projects along the rivers and the lack of knowledge about potential dangers on the part of local residents.

"Contradictions emanating from the infrastructure ministry's past policy of controlling floods by giving top priority to building dams came to a head, leading to a breaking of levees," says Hirotake Imamoto, a professor emeritus at Kyoto University who once headed the school's Disaster Prevention Research Institute.

His perspective was proven correct by last month's flooding of the Kinugawa River. Around Sept. 9, a weather phenomenon known as a linear precipitation zone appeared over the river, dumping a total of 660 mm of rain. From that day until the small hours of the following day, the ministry reduced the amount of water discharged from the Kawamata and Kawaji dams on the Kinugawa River and the Yunishigawa and Ikari dams on the Ojika River, which flows into the Kinugawa, to less than 10 percent of the normal level in some dams. Even though the ministry took these steps in line with relevant regulations, it nonetheless failed to prevent the flooding, Imamoto says.

During the period of high economic growth, the government made it a policy priority to construct dams as a way to promote and facilitate the use of water for the hydroelectric, agricultural and manufacturing sectors.

As it became less likely for water use to continue growing with the waning of hydroelectric power generation, the infrastructure ministry added "flood control" as another purpose for building dams so that new construction projects would be maintained. A good example is found in the current project to build the Yanba Dam on the Agatsumagawa River in Gunma Prefecture.

A newspaper reporter covering the infrastructure ministry says that since the flood control component of dam construction was adopted in a rush and with little forethought, the dams have failed to prevent disasters. But, he says, the ministry refuses to admit its mistake.

It is a simple fact, the reporter says, that no dam can cope when the amount of rainfall exceeds its capacity, and the country continues to be deceived by the ministry's childish attitude.

Imamoto says last month's flooding could very likely have been avoided had the ministry diverted portions of the river management budget to reinforcing existing levees. At the very least, he says, the damage caused by the levee collapses could have been reduced.

The ministry's budget related to flood control exceeds ¥800 billion a year. Although some of the money goes to improving levees, nearly ¥200 billion is being spent on useless dams. Completing construction on the Yanba Dam alone is going to cost no less than ¥1 trillion.

The aforementioned reporter says, moreover, that when criticism of the dam construction policy grew, the infrastructure ministry launched a "super levee" project that calls for elevating whole areas adjacent to a river so that the entire area would serve as a levee.

This is extremely costly, however, as evidenced by the fact that a whopping ¥4.7 billion will be poured into building a super levee only 120 meters long in Edogawa Ward, Tokyo. When a similar project in an adjacent area is taken into account, the total sum would run beyond ¥2 trillion. The project is expected to take 200 years to be completed.

If the super levee scheme is seen through, it could become an effective means of preventing floods. But if the nation's serious fiscal malaise is taken into consideration, the overall plan can only be described as "a pie in the sky." The biggest problem is that the ministry has been so bogged down with new dam construction and super levee ideas that it has failed to implement reinforcement of existing embankments.

There are ways to prevent embankments from collapsing without spending huge sums of money, says Imamoto. It has been proven, he says, that river embankments can be made strong enough to withstand floods if steel sheet piles are driven into the ground on both sides of them.

Although the ministry has been saying there are no effective means of reinforcing river embankments, this is an outright lie. The method Imamoto advocates worked effectively when a major tsunami struck northeastern Japan in the aftermath of the huge 2011 earthquake.

The cost of driving steel sheet piles is said to be about ¥1 million per meter of embankment, which is infinitesimally smaller than the ¥30 million needed to build the same length of super levee.

Why, then, is the infrastructure ministry reluctant to adopt the sheet pile method? A ministry insider points to two reasons: one is that the ministry fears being held accountable for pursuing policies centered on dam construction, and the other is that the super levee project would become unnecessary.

Therefore, it is no exaggeration to say that officials' eagerness to protect their own positions and interests led to the calamities of September.

Imamoto also points out that it was a big mistake to build houses in the area flooded last month because it is geologically depressed lowland. In the old days, that area was used for agriculture where farmers planted hedges to divert water and kept boats in their barns in case they had to flee floodwaters. Today, however, the residents have none of these preparations. Similar situations are found in many other parts of the country.

Last year, landslides in the city of Hiroshima caused great damage and many deaths. In the past, people had avoided living in these districts out of fear of landslides. The Japanese people are forgetting experiences and precautions needed to live safely with rain, rivers and land that can cause calamity. And the infrastructure ministry's culpability is obscured by the repeated excuse that the type of flooding that hit the Kinugawa River occurs only once every half a century.

Not only is it urgent for the government to review its river management policies, but the general public must also reflect on the notion — based on arrogance — that flooding is easy to control.

This is an abridged translation of an article from the October issue of Sentaku, a monthly magazine covering political, social and economic scenes.