Жапонияның Күма өзені

River in Kumamoto Prefecture, Kyūshū, Japan

The Kuma River (球磨川) is a river in Kumamoto Prefecture, central Western part of Kyūshū, Japan. It is sometimes referred as Kumagawa River. It is the longest river in Kyushu, with the length of 115 km long and has a drainage area of The river's estuary was designated part of Japan's 500 Important Wetlands. It is considered to be one of the three most rapid rivers of Japan (the other two being the Mogami River and the Fuji River). The Kuma River is classified as class A river, under the management of the Japanese government. The Kuma River is a popular tourist spot; about 70,000 people visit every year. Tourists are attracted to Ayu fish or sweetfish which inhabits at the Kuma river and some of its tributaries, where many people especially enjoy “shaku ayu”. The river is also used for fishing, mainly in June, and for irrigation of nearby rice fields. It then empties into the Yatsushiro Sea at Yatsushiro. The Kuma river is also known in relation to the Arase dam due to its removal project being the first dam removal in not only Japan but the whole of Asia. In 2020, the flooding of the Kuma River was a major incident in which a number of people from nearby areas were killed or seriously injured.

The Kuma River and its watershed covers nearly 25% of the entire area of Kumamoto Prefecture, and it is the largest river in the prefecture. The Kuma River begins its course from Mount Choushigasa flowing primarily through Kumamoto prefecture, leading to the Yatsushiro Bay. It is the only major and the largest river connected to the Yatsushiro sea. Before flowing into the Yatsushiro sea, where a large tidal flat is formed at its river mouth. Before flowing into the Yatsushiro sea, the Kuma River flows through the Hitoyoshi city, the Kuma village and the Yatsushiro city. The Kuma River flows through the Shimanto terrane and mainly through the Chichibu terrane. The Kuma River has 80 tributaries with its combined total length of 434 km. One of the major tributaries of Kuma River is Kawabe River, joining Kuma river at Hitoyoshi city, Kumamoto prefecture. The round shape of the Kuma River basin assists with water and sediment transport function. The upper stream of the Kuma River run through a steep gradient which later changes to medium gradient. It splits into multiple channels before flowing to the Yatsushiro Sea. The Kuma River is given the nickname of “Abaregawa” (meaning raging river) by the local Japanese people, due to its fast flowing nature. It is recognized as the three most rapid rivers in Japan, along with the Mogami River in Yamanashi prefecture and Fuji River in Nagano, Yamanashi and Shizuoka prefecture. Other major tributaries of the Kuma River include: Kudagiri River, Yoshio River, Imo River (Japan), Mae River, Mune River, Hatomune River, and Ogawauchi River.

Since as early as the Edo period (1603 1868), the Kuma river had a pivotal role in providing drinking water and as a source of food. Despite maintaining much of its natural landscape, the Kuma River and especially its basin area was largely impacted by human activities for economic and social development. The landscape of the Kuma river basin was subject to change from the later 17th century for economical and social development of its neighbourhood. During this time, the Kuma river was utilised as an important site for transportation in association to business, connecting the Yatsushiro city and the Hitoyoshi city. The Kuma River was actively used by the local feudal lords (daimyo). From these periods up until the 1900s, residents of the Kuma River neighbourhood often managed woodlands which created agricultural landscapes. Starting from approximately the Meiji era (1868 1912), slash and burn agriculture was active, in order to produce crops, including Japanese millet, azuki beans, sweet potato and taro. Until the late 20th century, wet rice cultivation of the primary factor of forming landscapes in the lower areas of the Kuma River. People often relied on the Kuma River for wet rice cultivation. Later in the 20th century, the landscapes of the Kuma river started to change due to constructions of large dams, including the Ichifusa dam, the Setoishi dam and the Arase dam for the purpose of controlling water related issues such as flood. In 1896, Japan implemented the River Act for management of water. In 1964, it was renewed for further control of water and its use, aiming to manage rivers in Japan including the Kuma River. The Kuma River is categorised as one of the A class rivers, strictly regulated under the Japanese government. The national level administrations of Ministry of land, Infrastructure, Transport and Tourism are in charge of management of the rivers of Japan.

The Kuma River has always been famous for the catching of Ayu, also known as sweetfish. The average length of Ayu in the Kuma River is 22.7 cm, with the weight at an average of 122g. However, the Ayu inhabiting around the dams have an average of 22 cm in length, and weighed 103g while Ayu inhabiting in the other sections of the river had an average length of 22 cm and weighed 103g. it is said that the number of Ayu in the area has decreased drastically due to human influences such as the constructions of the dams. Generally, from early March to May, Ayu swim into the Kuma River from the Yatsushiro Sea. The Kuma River and its tributary Kawabe River is known for its “shaku ayu”, a very large Ayu having a length of 30 cm which attracts many of its tourists. Fishing of Ayu is generally done from early summer to fall, economically assisting the locals in the surrounding of Kuma River especially for those running inns and restaurants. Freshwater eels, donko (Odontobutis obscura), as well as gane crabs (Eriocheir japonica) were also popular for fishing prior to the construction of dams on the Kuma River. The local fishermen have also mentioned that the weather loach (Misgrunus anguillicaudatus), the Chinese soft shell turtle (Pelodiscus sinensis) and the Japanese rice fish (Oryzias latipes) were often seen in the Kuma River before the construction of dams. The changes of water flow, water levels and the pollution of water caused the freshwater eels to leave the Kuma River areas. Due to severe impacts on the environment of the river, such as the disappearance of particular species, there have been debates over dam constructions from the 20th century. In 1999, fish ladders were built at the Arase dam and Setoishi dam but it did not lead to solving issues of decrease in the number of species along the Kuma River. Among the 50 deaths, 14 deaths were the residents of a nursing home located in the Kuma village, near the Kuma river. One of the areas nearby was flooded up to a depth of 4.3m. Shinzo Abe, Japanese prime minister at the time, responded to the flooding of the Kuma river by visiting the areas affected and assessing the aid needed. Financial aid for the areas with crucial damage, as well as restoration of highways and other damages caused by the Kuma river flooding was outlined. Prime Minister Abe assigned the aid of 400 billion yen as a support for repairing any damages as well as businesses affected by the flood. The Kuma River have also badly flooded in 1965, caused by heavy rainfall. It is also said that this flooding was worsened by the dams built along the Kuma River mainstream. Local residents have commented that flooding have become worse after the construction of dams, where flooded water became more muddy or polluted.