The Oldest Submerged Bridge on the Shimanto
The Ittohyo Submerged Bridge (一斗俵沈下橋, Ittohyo Chinkabashi) is a reinforced concrete bridge built in 1935 over the upper Shimanto River at Ittohyo, Shimanto Town, Takaoka District, Kochi Prefecture, which in 2000 was registered as a Registered Tangible Cultural Property.
The Agency for Cultural Affairs records a reinforced concrete girder bridge of nine spans, 61 metres long and 2.5 metres wide. The owner is recorded as Kubokawa Town, now part of Shimanto Town.
The Agency identifies it as the oldest surviving submerged bridge in the Shimanto River basin, and Shimanto Town describes it in the same way.
What a Submerged Bridge Is
The name chinkabashi, sinking bridge, comes from the way the bridge goes under the water when the river rises, as the Agency's description notes.
Such bridges have no parapets, so that floodwater and driftwood pass over them instead of catching. Built low on the assumption that they will be submerged, they have served as everyday roads along the Shimanto.
Shimanto Town notes that each of its submerged bridges reflects the period in which it was built, and that they were once lifelines for local people and are now where children play in the river.
What to Look For
The Agency notes that the depth of the girders varies with the length of each span. Look at the side of the Ittohyo Submerged Bridge from the bank to see the girders change slightly from one of the nine spans to the next.
The Agency also praises how well the bridge sits in the valley landscape. From the riverbank, the low deck without parapets lies quietly across the upper Shimanto.
Visiting the Ittohyo Submerged Bridge
Shimanto Town places the bridge beside Prefectural Road 19. It is still used as a road and has no parapets, so watch your footing and look out for vehicles when crossing or taking photographs. Keep away when the river is high and the bridge is under water.
Enquiries: Shimanto Town tourism and community section, 0880-22-3281.
Q&A
- When was the Ittohyo Submerged Bridge built?
- In 1935; it is the oldest surviving submerged bridge in the Shimanto River basin.
- What is a submerged bridge?
- A low bridge without parapets, built on the assumption that it will go under water when the river rises.
- How long is the Ittohyo Submerged Bridge?
- 61 metres long and 2.5 metres wide, with nine reinforced concrete spans.
- Where is the Ittohyo Submerged Bridge?
- At Ittohyo in Shimanto Town, Kochi Prefecture, beside Prefectural Road 19.
- How is the name Ittohyo read?
- Ittohyo; the bridge is called Ittohyo Chinkabashi in Japanese.
Basic Information
| Name | Ittohyo Submerged Bridge (一斗俵沈下橋) |
|---|---|
| Location | Ittohyo, Shimanto Town, Takaoka District, Kochi Prefecture |
| Designation | Registered Tangible Cultural Property (structure) |
| Year Designated | Registered 2000/12/4 (Heisei 12) |
| Quantity | 1 structure |
| Dimensions | Reinforced concrete nine-span girder bridge, 61 metres long, 2.5 metres wide |
| Owner | Kubokawa Town (now Shimanto Town) |
| Public Access | In use as a road; submerged in floods |
References
- Agency for Cultural Affairs Database: Ittohyo Submerged Bridge (Japanese)
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00002096
- Cultural Heritage Online: Ittohyo Submerged Bridge (Japanese)
- https://online.bunka.go.jp/heritages/detail/178316
- Shimanto Town: History and Culture (Japanese)
- https://www.town.shimanto.lg.jp/life/detail.php?hdnKey=1268
Last verified: 2026.09.27