The Sumiyoshi River is the main river of a secondary river system flowing through eastern Kobe, Hyogo Prefecture. Descending steeply from the foothills of Mount Rokko, it forms an alluvial fan before entering the urban area. In its middle and lower reaches, the river flows through an elevated channel, a distinctive geographical feature known as a raised riverbed or an “aboveground river.”
Despite flowing through a densely populated urban area, the Sumiyoshi River is remarkably clean. Its steep gradient and the limited inflow of domestic wastewater help maintain water quality good enough to support fireflies. The river’s pure water has also contributed to sake production in Nada Gogo, one of Japan’s most famous sake-brewing regions.
A running path along the river provides residents with a pleasant place to exercise, walk, and relax. The riverbanks are also lined with large residences, forming part of the elegant residential districts associated with Hanshinkan Modernism, a cultural movement that flourished between Kobe and Osaka. Historic buildings, including Isho-an, the former residence of novelist Junichiro Tanizaki, offer glimpses into the area’s architectural and cultural heritage.
The Sumiyoshi River originates on the southern slopes of Mount Rokko, which rises to 931 meters. In its upper reaches, it follows a fault valley extending southwest between the Otsuki Fault near the main ridge of Mount Rokko and the Gosukebashi Fault near the ridgelines of Mount Uchikoshiyama and Mount Arijiyama. Over time, the river has deeply eroded the surrounding mountains. At Gosuke Dam, it changes direction and flows southward.
The Gosukebashi Fault takes its name from a former bridge called Gosuke-bashi, which once stood near the present dam. The bridge was located along the Sumiyoshi Road, also known as the Arima Highway, which crossed the valley in this area. The pronounced semicircular bend where Gosuke Valley joins Sumiyoshi Valley is believed to be related to the fault.
After leaving the mountainous area, the Sumiyoshi River is joined by the Nishitani River and continues through the city. In the middle and lower reaches, the riverbed lies above the surrounding land. The Tokaido Main Line passes beneath the river through a tunnel, while the Rokko Island Line runs alongside the river from this section toward the coast.
The river passes west of Isho-an, the former residence of Junichiro Tanizaki, and continues beyond Hanshin Uozaki Station. With Rokko Island visible ahead, it eventually empties into Osaka Bay near Higashi-Kobe Port.
Fed by water descending from Mount Rokko, the Sumiyoshi River has a substantial drop in elevation and flows swiftly. Over centuries, it transported large quantities of sediment from the mountains, gradually creating a broad, gently sloping alluvial fan. Settlements developed on this fertile land long before the Edo period.
As embankments were built to protect these settlements from flooding, sediment accumulated within the river channel. The riverbed gradually rose above the surrounding ground, accelerating the development of the elevated channel that characterizes the middle and lower reaches today.
The Sumiyoshi River has caused repeated floods throughout its history. In 1504, an event known as the Jimeiji Flood swept away the large Jimeiji Temple on the river’s western bank. Historical records also document flooding in 1544, 1608, 1776, 1782, 1789, 1799, 1813, 1848, 1881, 1885, 1896, 1899, 1903, 1905, 1910, 1921, 1922, 1925, and 1935.
One of the most devastating disasters was the Great Hanshin Flood of 1938, which caused extensive damage throughout the surrounding area. Huge rocks and uprooted trees carried down from Mount Rokko became lodged against the Sumiyoshi River railway bridge on the Hankyu Kobe Line. The resulting obstruction blocked the flow of water and contributed to the river’s overflow.
Following the disaster, the riverbed and embankments were raised, and the Hankyu Kobe Line was restored to cross the elevated channel. These changes reshaped the local landscape and affected the area’s transport infrastructure.
In the early Meiji period, when the government built the railway line now known as the Tokaido Main Line, a tunnel was constructed beneath the Sumiyoshi River. The source identifies this as Japan’s first railway tunnel, highlighting the river’s place in the history of the country’s railway development.
During the Taisho period, construction of the Hanshin National Highway, now National Route 2, included dredging work on the Sumiyoshi and Ishiya rivers. Lowering the riverbeds made it possible to open the Hanshin National Route Line, a streetcar service. In some sections of the Sumiyoshi River, however, excavation could not be completed sufficiently. Stepped sections of the riverbed were therefore used to help control the speed of the current.
After the Great Hanshin Flood of 1938, further changes to the riverbed and embankments influenced the surrounding roads and railways. The Sumiyoshi River remains an important part of the area’s urban landscape and transport history.
Today, the Sumiyoshi River continues to provide a welcome natural retreat amid the urban landscape of Kobe. Its clear water, riverside running path, and green surroundings make it a popular place for residents to enjoy the outdoors. The elegant residential neighborhoods along its banks preserve traces of the area’s historical development, while the river itself remains closely connected to local nature, culture, and everyday life.