The beautiful Tonda River flows through Kamitonda Town in Wakayama Prefecture, and along its course are several unusual bridges known as submersible bridges. These bridges are deliberately designed to become submerged when the river rises during floods. In other parts of Japan, particularly along the Shimanto River in Kochi Prefecture, similar structures are often called “chinka-bashi,” or sinking bridges.
Several submersible bridges can be found along the Tonda River, but one of the best known is Sanno Bridge. Its narrow deck and complete lack of railings create a distinctive appearance that blends beautifully into the surrounding landscape. In recent years, the bridge has also become a popular destination for photographers and travelers looking for unique Japanese scenery.
Features of Sanno Bridge
Sanno Bridge connects the Sanno district with Hongo in Ikuma, crossing the calm waters of the Tonda River. Unlike conventional bridges, it has no railings or handrails.
The bridge is quite narrow, with only enough space for people to carefully pass one another. When standing on the bridge, the surface of the river is immediately beside you, creating the unusual sensation of walking directly above the water.
This combination of openness and gentle excitement has made Sanno Bridge popular with visitors and photography enthusiasts. On clear days, the blue sky, flowing river, and surrounding mountains come together to create a peaceful landscape reminiscent of traditional rural Japan.
The bridge has also attracted attention on social media because of its distinctive appearance. For travelers looking for an atmospheric and photogenic location away from the major tourist centers, Sanno Bridge offers a memorable experience.
Why Were Submersible Bridges Built?
The Tonda River has historically been prone to flooding. During periods of heavy rain, a conventional bridge with tall railings and other structures can catch floating logs and debris, increasing the pressure placed on the bridge and potentially causing serious damage.
A submersible bridge takes a different approach. By eliminating railings and keeping the structure relatively low, the bridge reduces the resistance created by fast-moving floodwater and allows water and debris to pass over it more easily.
Sanno Bridge was originally a wooden bridge and was repeatedly damaged or washed away by floods. It was later improved using ideas inspired by the sinking bridges of the Shimanto River in Kochi Prefecture. The bridge was eventually rebuilt as a stronger reinforced-concrete structure designed to withstand the region’s challenging river conditions.
A Bridge That Supports Local Life
Sanno Bridge is not simply a sightseeing attraction. It has long served as an important local transportation route and agricultural road, supporting the everyday lives of people in the surrounding communities.
In 1960, a bridge using concrete piles was constructed, but it was later washed away by flooding. The structure was subsequently strengthened, and in 1966 it was further improved by deeply embedding the bridge piers. In 1977, the bridge was extended, bringing its total length to approximately 138.5 meters.
This history reflects the practical knowledge and ingenuity of local communities that have lived alongside the Tonda River for generations. Rather than attempting to completely control the river, the bridge was designed to work with the natural behavior of the river.
The Natural Beauty of the Tonda River
The Tonda River is known as one of the few major rivers in Wakayama that has no dams along its main course. It is celebrated for its clear water and rich natural environment, providing habitats for freshwater fish such as ayu and amago trout.
The landscape around the submersible bridges changes beautifully throughout the year. Spring brings fresh green foliage, summer is ideal for enjoying the river and surrounding countryside, autumn brings colorful leaves, and winter offers crisp air and peaceful scenery.
Looking down from Sanno Bridge, visitors can enjoy the clear flowing water and surrounding mountains. The gentle movement of the river creates a soothing atmosphere, while sunset can transform the surface of the water into a beautiful golden landscape.
Submersible Bridges and the Kumano Kodo
Kamitonda Town occupies an important position in the history of the Kumano Kodo, the network of ancient pilgrimage routes that leads through the Kii Peninsula to the sacred sites of Kumano. The area lies near the traditional junction of the Nakahechi and Ohechi routes and has long been known as Kuchi-Kumano, or “the entrance to Kumano.”
Historic sites connected with the Kumano Kodo can be found around the area, including the remains of Yagami-oji and Inabane-oji, both associated with the pilgrimage tradition and recognized as part of the World Heritage-listed “Sacred Sites and Pilgrimage Routes in the Kii Mountain Range.”
The combination of traditional rice fields, the clear Tonda River, surrounding mountains, and unusual submersible bridges creates a landscape that gives visitors a sense of old Japan.
Walking through the countryside and crossing a submersible bridge is a particularly enjoyable way to experience the relationship between the Kumano pilgrimage routes, local communities, and the natural environment.
Hatayama Bridge: Another Submersible Bridge
Kamitonda Town is also home to another notable submersible bridge, Hatayama Bridge. It connects the Iwata and Ichinose districts and is approximately 174 meters long, with its deck around 4.5 meters above the normal river surface.
Like Sanno Bridge, Hatayama Bridge has no railings and is only about 1.5 meters wide. Crossing it provides a different perspective of the Tonda River and the surrounding mountains, making it another popular spot for visitors interested in unusual bridges and rural scenery.
For travelers with time to explore the area, visiting both Sanno Bridge and Hatayama Bridge offers an excellent opportunity to see how these distinctive structures have become part of the landscape and local way of life.
A Nostalgic View of Rural Japan
The appeal of a submersible bridge goes far beyond its unusual engineering. These bridges embody the history, practical wisdom, and lifestyle of communities that have lived alongside rivers for generations.
Walking slowly across the narrow bridge and watching the river flow below can provide a refreshing break from the pace of modern life. Without tall railings or large structures obstructing the view, visitors can feel unusually close to the water and surrounding landscape.
The quiet countryside, clear river, mountains, and traditional agricultural scenery create an atmosphere that can feel far removed from Japan’s busy cities. For international travelers, Sanno Bridge is a wonderful opportunity to experience a more peaceful and authentic side of rural Wakayama.
Access to Sanno Bridge
By Train
From Asso Station on the JR Kisei Main Line, Sanno Bridge is approximately a 15-minute walk.
By Car
The bridge is approximately 5 minutes by car from Kamitonda Interchange and approximately 15 minutes from Nanki-Shirahama Interchange.
Access to Hatayama Bridge
By Train
Hatayama Bridge is approximately a 20-minute walk from Asso Station on the JR Kisei Main Line.
By Bus
From JR Kii-Tanabe Station, take a local bus and get off at the Kami-Iwata bus stop. Hatayama Bridge is approximately a 3-minute walk from the bus stop.
By Car
Hatayama Bridge is approximately 10 minutes by car from Kamitonda Interchange and approximately 15 minutes from Nanki-Shirahama Interchange.
Experience the Quiet Beauty of the Tonda River
Sanno Bridge is a unique destination where Japanese engineering, local history, the Kumano Kodo, and beautiful river scenery come together. Its simple design reflects generations of local knowledge about living alongside a flood-prone river, while its narrow deck and lack of railings create an unforgettable way to experience the landscape.
For visitors exploring the Kumano Kodo or the southern Wakayama region, a stop at Sanno Bridge provides a chance to slow down and appreciate the peaceful scenery of the Tonda River. Combined with nearby historic pilgrimage sites and Hatayama Bridge, it offers a fascinating glimpse into the relationship between people, rivers, and the rural landscape of Japan.