The Hii River is a major river flowing through eastern Shimane Prefecture and western Tottori Prefecture. It is the principal river of the Hii River system and one of the most important waterways in the Izumo region.
The river rises at Mount Funatsu in the Chugoku Mountains and flows for approximately 153 kilometers. Its watershed covers more than 2,000 square kilometers. The river supplies water to the fertile Izumo Plain before flowing into Lake Shinji, then through the Ohashi River, Lake Nakaumi, and the Sakai Channel before eventually reaching the Sea of Japan.
The Hii River has been closely connected with the lives of local people for centuries. In the ancient Japanese chronicle Kojiki, it appears as the “Hi-no-kawa,” while the Izumo Fudoki refers to it as the “Izumo Okawa,” or Great River of Izumo.
Because the river is deeply connected with Japanese mythology, traditional industries, flood control, agriculture, and everyday life, exploring the Hii River offers much more than simply enjoying a beautiful natural landscape.
The Hii River is widely associated with the famous Japanese myth of Yamata-no-Orochi, the eight-headed and eight-tailed serpent. According to the legend, the deity Susanoo-no-Mikoto defeated the great serpent after arriving in the land of Izumo.
The myth is often interpreted as being connected with the repeated flooding of the Hii River. Since ancient times, the river has brought both benefits and danger to the communities along its banks. Its abundant water supported agriculture and daily life, while severe floods could cause widespread damage.
For this reason, the Hii River can be experienced not only as a natural landmark but also as a place where visitors can connect with the world of Japanese mythology and the long relationship between people and nature.
One of the most distinctive characteristics of the Hii River is its “tenjō-gawa”, or raised riverbed. This refers to a river whose bed has gradually become higher than the surrounding plain. Such landscapes are relatively rare in Japan.
The formation of this unusual landscape is closely connected with the traditional tatara ironmaking industry that once flourished in the surrounding mountains.
Tatara ironmaking used iron sand as its raw material. To obtain this iron sand, people developed a technique known as kanna nagashi. Mountain slopes were excavated and large quantities of soil and water were moved so that iron sand could be separated according to differences in density.
This process caused substantial amounts of sediment to flow into the Hii River. Over many years, the sediment accumulated on the riverbed, gradually raising it above the surrounding plain and contributing to the formation of the raised river landscape seen today.
The resulting terrain provides a fascinating example of how traditional industry and the natural environment became closely intertwined in the Izumo region.
The Hii River has experienced repeated flooding throughout its history, and communities along the river have developed increasingly sophisticated methods of controlling its waters.
During the Edo period, major flood-control projects known as kawatagae, or river diversions, were carried out. Particularly significant work followed major floods during the Kan’ei era, when the course of the Hii River was changed from its former westward route to an eastward route leading toward Lake Shinji.
This enormous engineering project moved the lakeshore forward by approximately 5 kilometers, creating new land that could be developed and used by local communities.
Another important feature of the region’s water-management history is a waterway known as Namazu-no-O. It was designed to draw water efficiently along the river embankment.
Its basic function has continued to the present day, representing the practical knowledge and ingenuity of the people who lived alongside the Hii River. These historic water-management systems demonstrate how closely the development of the Izumo Plain was connected to the river.
The Hii River basin encompasses a remarkable variety of landscapes, from mountain areas in the upper reaches to basins in the middle section, the broad Izumo Plain downstream, and the lakes and waterways near its mouth.
This diversity provides habitats for a wide range of plants and animals, making the river basin an interesting destination for nature observation.
Ayū sweetfish and salmon migrate upstream through the river, contributing to the region’s rich aquatic resources. Historical records also describe driftwood being carried downstream during spring, offering another reminder of the long-standing interaction between the river’s natural processes and human activities.
The Hii River is an essential source of water for agriculture and daily life in the Izumo Plain. Because its riverbed is higher than parts of the surrounding plain, managing and distributing water has historically presented challenges.
Local communities developed techniques such as mizuyose, which helped make more effective use of the river’s water for agriculture.
Through these innovations, the Hii River basin has supported communities for centuries. From ancient times to the present day, the fertile plain has developed as an important center of political, cultural, and economic activity in the Izumo region.
Today, the Hii River is an appealing destination for travelers who want to experience both nature and history. Numerous bridges cross the river, and each offers a different perspective of the surrounding landscape.
Among them, low-water bridges designed to withstand flooding offer particularly distinctive scenery. Their simple structures and close relationship with the river create a peaceful atmosphere that is well suited to photography and leisurely exploration.
The scenery along the Hii River changes throughout the year. Spring brings fresh greenery and renewed life to the riverbanks. In summer, the clear flowing water provides a refreshing atmosphere. Autumn brings colorful foliage to the surrounding landscape, while winter creates a quiet scene with a distinctly different character.
Visitors can combine a drive or riverside walk with nearby shrines, mythological sites, hot springs, and nature parks. Exploring several destinations along the river is an excellent way to discover the deeper cultural landscape of Izumo.
The Hii River is far more than a river. Its waters have shaped the landscape of Izumo, supported agriculture and communities, influenced traditional industries, and inspired some of Japan’s best-known mythology.
The history of tatara ironmaking, the landscape created by sediment, and the centuries of flood-control efforts all reveal how people have adapted to and worked with the river’s powerful natural forces.
At the same time, the Hii River remains a beautiful natural environment where visitors can enjoy changing seasonal scenery and explore the stories of ancient Izumo.
When traveling through the Izumo region, take time to follow the Hii River and discover the landscapes, traditions, and legends that have developed along its banks. It is an excellent way to gain a deeper understanding of the relationship between nature, mythology, industry, and everyday life in Izumo.