The Kuma River is a Class A river flowing through southern Kumamoto Prefecture on the island of Kyushu. It is counted among Japan’s Three Great Rapids, together with the Mogami River and the Fuji River. The river passes through the Hitoyoshi Basin, receives tributaries including the Kawabe River, crosses the Yatsushiro Plain, and eventually empties into Yatsushiro Sea, also known as Shiranui Sea.
It is the largest river in Kumamoto Prefecture and is celebrated for its dramatic scenery. Its beautiful landscapes have also earned it a place among Japan’s Twenty-Five Scenic Views.
In the past, the Kuma River was difficult to navigate because of its swift current and numerous enormous rocks. In 1662, during the Kanbun era, Masamori Hayashi, an uncle of Yorikata Sagara, the 22nd head of the Sagara clan, invested his own money in a project to open a navigable route through the river. By 1665, riverboats were able to travel along it.
Following these improvements, the river became a major route for transportation, trade, and distribution between the region and the outside world. It also played an important role in the sankin-kotai system, under which feudal lords traveled periodically to Edo, present-day Tokyo, to serve the shogunate. The river therefore contributed significantly to the development of the surrounding communities.
River transport gradually declined as the Hisatsu Line railway opened, roads improved, the forestry industry contracted, and dams were built. Today, the river is primarily associated with sightseeing boat trips and other tourism activities rather than commercial river transport.
The Kuma River continues to play an important role in the region’s economy. Its water supplies approximately 14,000 hectares of farmland, supporting agriculture throughout the river basin.
In the coastal industrial area of the Yatsushiro Plain, the river also supplies water for industries including papermaking, pulp production, and metal processing. In addition, its water resources are used by 20 hydroelectric power facilities distributed throughout the basin.
Near the mouth of the Kuma River, where it flows into Yatsushiro Sea, tidal flats covering more than 1,000 hectares spread across the coastal landscape. These wetlands are included in Japan’s Important Wetlands 500 list and attract more than 90 species of wild birds throughout the year.
The area is well known among birdwatchers and is also designated an Important Bird Area (IBA). Its extensive tidal flats provide valuable habitats for wild birds and form an important part of the natural environment of the Yatsushiro coast.
The Kuma River’s headwaters are located near Sekinagi Pass, at an elevation of 1,391 meters, and Mizukami Pass, at 1,458 meters, in Mizukami Village, Kuma District. From its mountainous source area, the river flows westward through the Hitoyoshi Basin and across agricultural land.
It then passes through narrow valleys in the Kyushu Mountains before reaching the Yatsushiro Plain. The landscape changes considerably along its course, ranging from powerful rapids to calmer stretches of water. This varied terrain is one of the defining features of the river.
The exact origin of the river’s name is not known. In the early Meiji period, several different written forms were used, including “求麻,” “求磨,” and “球磨.”
The 1772 chronicle Higo Nisshi records possible explanations for the name. One theory describes it as a river with an enormous number of tributaries, while another suggests that it was named after Kuma District, from which the river flows. These explanations have been passed down as possible origins of the name.
The Kuma River’s powerful currents and the heavy rainfall that affects its basin have repeatedly caused serious disasters. From 1669 through 2020, the region experienced numerous major floods and inundation events.
One particularly devastating disaster occurred in 1755, when a landslide-created lake burst through its natural barrier, causing a catastrophic flood known as a mountain tsunami. Approximately 500 people died. Major flooding also occurred during the 1965 Kuma River disaster and the July 2020 heavy rains, when widespread inundation caused extensive damage and loss of life.
In July 2020, exceptionally heavy rainfall caused the Kuma River to overflow its banks. The Chiju-en special nursing home was inundated, and 14 residents died. The disaster claimed a total of 66 lives in Kumamoto Prefecture and caused widespread damage.
Hitoyoshi City and Yatsushiro City were among the areas affected by extensive flooding. Homes, infrastructure, businesses, and local communities suffered serious damage, leaving a profound impact on the region.
Flood control along the Kuma River has long been a subject of debate. As described in the source article, as of 2021 the river was the only one among Japan’s 109 Class A river systems without a river improvement plan in place. This situation reflected local support for flood control measures that did not rely on dams.
After the July 2020 disaster, however, concerns were raised about the limitations of flood control strategies that do not depend on dams. The national government and local authorities have continued discussions about future measures to reduce flood risk and protect communities along the river.
The Kuma River is deeply connected to the natural environment, history, and economy of southern Kumamoto. Its dramatic rapids and scenic valleys have made it one of Japan’s most celebrated rivers, while its water has supported transportation, agriculture, industry, and power generation for centuries.
At the same time, the river’s powerful currents and flood history have brought repeated challenges to the communities along its banks. The devastating July 2020 disaster renewed discussion about how to balance the river’s natural character with the need to protect lives and property.
The future of the Kuma River depends on finding ways to preserve its landscapes and ecological value while improving safety for the people who live in its basin. Visitors can appreciate its remarkable scenery, but should also remain aware of weather conditions and official safety information when exploring the river and surrounding areas.