Ichifusa Dam is a multipurpose dam located in Mizukami Village, Kuma District, Kumamoto Prefecture. Built on the main stream of the Kuma River system, it is a gravity-type concrete dam standing 78.5 meters high. The dam was formerly known as Shinbashi Dam.
The reservoir created by the dam is called Lake Ichifusa. Approximately 10,000 cherry trees have been planted around the lake, making it one of the most famous cherry blossom destinations in Kumamoto. It has also been selected as one of Japan’s 100 Best Cherry Blossom Spots.
In addition to its beautiful scenery, the dam plays an important role in flood control, agricultural water supply, and hydroelectric power generation. It is an important part of the water infrastructure supporting the Kuma River basin.
Ichifusa Dam is situated in the upper reaches of the Kuma River, near its confluence with the Yuyama River. Approximately 1.2 kilometers downstream is Kōno Dam, which works together with Ichifusa Dam as part of the regional water management system.
The reservoir, Lake Ichifusa, lies at the foot of Mount Ichifusa. The surrounding landscape combines the lake, mountains, forests, and seasonal flowers, making the area a popular destination for sightseeing and outdoor recreation.
The construction of Ichifusa Dam was planned in response to serious flooding and water shortages in the Kuma River basin. During the postwar period, several typhoons, including Typhoon Della, Typhoon Faye, and Typhoon Judith, caused severe damage to the region. Flood prevention had become an urgent issue.
At the same time, the area faced shortages of agricultural water and electricity. A multipurpose dam was therefore considered necessary to address these problems and support regional development.
Preparatory work and surveys began in 1949. Construction work began in 1953, and work on the main dam structure started in 1957. Ichifusa Dam was completed in 1960. Kōno Dam, located downstream, was also completed around the same period.
In 1961, the facilities were transferred to the Kumamoto Prefectural Government. Since then, Ichifusa Dam has been operated as a prefectural facility serving several important purposes in the Kuma River basin.
One of the main purposes of Ichifusa Dam is to reduce the risk of flooding along the Kuma River. The dam regulates the amount of water released downstream during periods of heavy rainfall.
Under its planned flood-control operation, the dam can reduce a planned peak inflow of 1,300 cubic meters per second to 650 cubic meters per second. At Hitoyoshi, farther downstream, the planned reduction is from 4,500 cubic meters per second to 4,000 cubic meters per second.
Ichifusa Dam was the first dam in Japan to introduce an automatic water-level maintenance system and an automatic flood-control system. Manufactured by Hitachi, these systems help regulate the amount of water released when inflow increases rapidly.
These automated systems were an important technological feature of the dam and were introduced to improve the management of water levels and flood-control operations.
Ichifusa Dam also plays an important role in providing irrigation water to farmland along the left bank of the Kuma River.
It supplies water to approximately 3,578 hectares of agricultural land, with a maximum supply capacity of 15.6 cubic meters per second. Of this area, approximately 2,572 hectares are rice paddies and 1,006 hectares are fields used for other crops.
The reservoir helps maintain a stable supply of water for farming, supporting agricultural production throughout the region.
Hydroelectric power is another important function of Ichifusa Dam. Two power stations operated by the Kumamoto Prefectural Enterprise Bureau use water from the dam to generate electricity.
Ichifusa No. 1 Power Station has a maximum output of 15,100 kilowatts, while Ichifusa No. 2 Power Station has a maximum output of 2,300 kilowatts. Together, they generate approximately 50 million kilowatt-hours of electricity annually.
After water is used at Ichifusa No. 1 Power Station, it flows downstream to Kōno Dam, where the discharge is adjusted. This system helps regulate the flow of water after power generation.
The construction of Ichifusa Dam required substantial land acquisition and changes to the surrounding community. A total of 132.6 hectares of land was acquired, and 208 houses were relocated.
Compensation was also provided for facilities and activities affected by the project, including the Mizukami Village government office, schools, power-generation facilities, and fishing-related interests.
These measures were part of the effort to address the impact of dam construction on the local community while proceeding with the development of the water-control infrastructure.
The development of Ichifusa Dam also affected the area’s earlier hydroelectric facilities. The Shinbashi Power Station, which had been operated by Kuma River Electric Company since 1927, was discontinued in connection with the dam construction project.
The facility was subsequently operated by Kyushu Electric Power until 1959. Its history reflects the changes in regional electricity production that accompanied the construction of the new dam and power stations.
In July 1965, five years after Ichifusa Dam was completed, severe flooding occurred along the Kuma River. Emergency water releases were carried out during the event, but misunderstandings about the releases spread among local residents and led to growing distrust of the dam.
This experience highlighted the importance of clear communication about dam operations and the need to build public confidence in flood-control facilities.
During the heavy rainfall of July 2020, water levels in the reservoir rose dramatically despite advance water releases. The reservoir approached the level at which emergency releases would have been necessary.
The event raised questions about the flood-control capacity of the dam. The dam operator explained that a major factor behind the flooding was the large amount of water flowing into the Kuma River from its tributaries.
The disaster renewed public attention to flood prevention and the challenges of managing a river system during extremely heavy rainfall. It also demonstrated the importance of considering water flowing in from tributaries, not only the main river, when assessing flood risks.
Various proposals have been considered over the years to improve the dam’s performance, including redevelopment projects and the construction of additional discharge channels. However, these plans involve challenges related to their effectiveness and financial costs.
The future management of Ichifusa Dam remains an important issue for regional disaster-prevention planning, water resources, agriculture, and electricity supply.
For visitors, the most famous attraction around Ichifusa Dam is the cherry blossom scenery of Lake Ichifusa. Approximately 10,000 cherry trees grow around the reservoir, creating a beautiful display when they bloom in spring.
The lake and surrounding mountains provide a picturesque background for the blossoms. The area is especially popular during the cherry blossom season, when visitors come to enjoy the flowers and the peaceful lakeside scenery.
Because the lake is recognized as one of Japan’s 100 Best Cherry Blossom Spots, it is a particularly appealing destination for travelers interested in seasonal landscapes and photography.
Visitors interested in infrastructure and engineering can collect an official dam card for Ichifusa Dam. The cards are distributed at the dam management office. A separate card for Kōno Dam is available at the Kōno Dam lookout station.
Lake Ichifusa is also used for recreational fishing, including bass fishing. The reservoir attracts anglers who enjoy fishing in a mountain setting.
The dam has also become known among fans of the Japanese anime series Natsume’s Book of Friends, in which Ichifusa Dam appears. The connection has added another reason for some visitors to explore the area.
By public transportation, take the Yunomae Line of the Kumagawa Railway to Yunomae Station. From there, transfer to a Kyushu Sanko Bus bound for Ichifusa Tozanguchi and get off at the Dam Site bus stop.
By car, Ichifusa Dam is approximately 30 kilometers from the Hitoyoshi-Kuma Smart Interchange on the Kyushu Expressway. Visitors can reach the area via National Route 388 or Kumamoto Prefectural Route 142.
Whether visiting for the cherry blossoms, lakeside scenery, fishing, or an interest in dam engineering, Ichifusa Dam offers a distinctive combination of natural beauty and regional infrastructure. It is also a place where visitors can learn about the relationship between the Kuma River and the communities that depend on it.