Pre-1967 river administration

At the beginning of the Meiji era, river construction mainly consisted of low water construction such as securing water for boat transportation and irrigation, but after the middle of the Meiji era, boat transportation declined with the spread of railways, and on the other hand, development of river coasts exacerbated damage from floods. As the number of floods increased, a shift was made to high water construction to prevent flooding by building levees.^[3]

The old system was enacted in 1891 following the proclamation of the Meiji Constitution. As Japan's first modern public property management system, a systematic legal system for river management was established. However, due to the background of its enactment, the old River Law had strong overtones of control by state power, and, reflecting the social situation at the time, placed more emphasis on flood control than water utilization.^[3]

New River Act

Over the following 70 years, due to post-war social and economic development, the use of river water for hydroelectric power generation and industrial water increased rapidly^[3] and because of inconsistencies that had arisen in the system implemented by the old River Act, the new River Act was enacted in 1962, with the following changes:

• All rivers and river systems are classified into four classes^[3]
• Entities in charge of rivers are required to formulate a plan for integrated water management^[3]
• Establishment of regulations related to water use^[3]
• Establishment of regulations to prevent disasters caused by dams^[3]

1997 amendment

The River Act was amended in 1997, changing its text to have a greater emphasis on conservation of natural environments, and the consultation and participation of local residents in forming water management plans.^[4]

Impact

The 1967 River Act simplified the management of waterways in Japan by merging previously separate systems into one unified water management system.^[3][5] Before this, the river management system in Japan was seen as heavy-handed and overly bureaucratic.^[5] Especially post-1997 amendment, there is now greater community involvement when formulating plans regarding rivers and water management.^[4]

List of Class A river systems

The number of dams only includes existing and unestablished dams that meet the criteria (15 metres (49 ft) or more in bank height) of the River Law. The management entity is irrelevant. The number in parentheses is the number of dams on the main river, excluding tributaries. The number of dams does not always exceed the number of hydroelectric plants because plants with intake weirs less than 15 metres (49 ft) high are not considered dams. The acronym BOD refers to biochemical oxygen demand.

Note: Okinawa has no Class A rivers.