What Is Bannai River No. 1 Sabo Dam?
Bannai River No. 1 Sabo Dam (万内川一号堰堤, Bannaigawa Ichigō Entei) is a rubble-concrete sabo dam built around 1921 on the Bannai River in Nishinoya, Myoko City, Niigata Prefecture, and was registered as a Registered Tangible Cultural Property on March 18, 2003.
A sabo dam is a check dam built across a mountain stream to trap sediment and slow debris flows before they reach the villages below. Of the registered dams on the Bannai, this is the one farthest downstream. It measures 43 meters along the crest and stands 5.0 meters high, a gravity dam of rubble concrete with stone revetments on both banks below it and a small secondary dam just in front that catches the water falling from the notch. It was remodeled around 1933.
Niigata Prefecture dates the construction of Bannai River No. 1 Sabo Dam to 1921 through 1923, and its explorer map for the valley describes it as the prefecture's first sabo dam, raised over three years by local people from boulders split on site.
Why It Was Registered
The dam was registered under the criterion of contributing to the historic landscape of the country. The Agency for Cultural Affairs notes that its downstream face leans back at a batter of 1:0.3 (0.3 horizontal for every 1 vertical), gentler than the other Bannai dams of the same period, and that its crest is unusually thick, making the whole structure especially solid. The agency also counts Bannai River No. 1 Sabo Dam among the early examples in Japan of a sabo dam in rubble concrete.
Rubble concrete means large stones packed into a concrete mass. According to the prefecture's explorer map, cement was expensive at the time and was used only for the No. 1 and No. 2 dams; the dams further upstream were laid as dry stone (Karazumi). No. 1 is therefore built differently from the stone series that climbs the valley behind it.
What to Look For
Stand facing the dam and you can follow the water: it drops through the notch, is caught at once by the secondary dam, and then runs downstream between the revetments. The Agency for Cultural Affairs singles out the fact that the main dam, secondary dam and revetments all survive in good condition.
Look at the crest, too. Compared with the stone dams upstream, the crest of Bannai River No. 1 Sabo Dam is broad and its downstream face lies back further, a heavier build for the last barrier above the village.
The nearby Viewpoint 1 stands on what was once farmland known as Segawara. The prefecture's explorer map says that nearly 30 meters of sediment piled up here in 1902, and it prints a photograph of the newly finished dam beside a present-day view from the same spot. With the map in hand, you can compare the bare, ravaged riverbed of the old picture with the wooded valley you see today.
How to Visit
Bannai River No. 1 Sabo Dam is the first registered dam you reach when walking up from the park, and it makes a natural starting point for the path to the No. 3 and No. 4 dams. The prefecture's explorer map of dams No. 1 to No. 4 can be downloaded from its website.
Bannai River No. 1 Sabo Dam stands in the open and can be viewed freely from the path; neither the prefecture nor the city lists any restriction on photography. It is a working sabo structure, so stay off the crest and the spillway notch, and keep back from the water after heavy rain. Opening season and directions to Bannai River Sabo Park are covered on the Bannai River Sabo Facilities page.
- 📍 Plan Your Visit to Niigata
- Find tours, activities & transport passes near Bannai River No. 1 Sabo Dam
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Q&A
- When and why was Bannai River No. 1 Sabo Dam built?
- It was built around 1921 as part of Niigata Prefecture's first sabo project, launched after Mount Awadachi collapsed in 1902 and a debris flow destroyed much of Nishinoya. Its job is to hold back sediment coming down the valley and protect the village and its fields.
- Why is Bannai River No. 1 Sabo Dam a Registered Tangible Cultural Property?
- It was registered on March 18, 2003, as a structure contributing to the historic landscape. The Agency for Cultural Affairs points to its solid build, with a gentle downstream batter and a thick crest, and to its place among the early rubble-concrete sabo dams in Japan.
- Can I visit Bannai River No. 1 Sabo Dam, and is there a fee?
- Yes. It stands outdoors and can be seen freely from Bannai River Sabo Park and the riverside path. The park is open from April to November and is free.
- Where is Bannai River No. 1 Sabo Dam?
- Bannai River No. Directions to Bannai River Sabo Park are on the Bannai River Sabo Facilities page.
- Is the Bannai River No. 2 dam also registered?
- No. According to the prefecture, 11 of the 18 sabo dams on the Bannai were registered: No. 1, No. 3, No. 4, No. 6, No. 7, No. 8 and No. 10 through No. 14. The No. 2 dam is not among them.
Basic Information
| Name | Bannai River No. 1 Sabo Dam (万内川一号堰堤) |
|---|---|
| Location | Nishinoya, Myoko City, Niigata Prefecture |
| Designation | Registered Tangible Cultural Property (Structure), Registration No. 15-0145 |
| Year Designated | Registered 2003/3/18 (Heisei 15) |
| Quantity | 1 structure |
| Dimensions | Crest length 43 meters, height 5.0 meters |
| Owner | Niigata Prefecture |
| Public Access | Outdoors and freely viewable; Bannai River Sabo Park is open April to November, free of charge |
References
- Agency for Cultural Affairs, Database of National Cultural Properties: 万内川一号堰堤
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00003212
- Cultural Heritage Online: Bannai River No. 1 Sabo Dam
- https://online.bunka.go.jp/heritages/detail/168522
- Niigata Prefecture: Bannai River stone sabo dams (Registered Tangible Cultural Properties)
- https://www.pref.niigata.lg.jp/sec/jouetsu_sabou/bunkazai-bannai.html
- Niigata Prefecture: Explorer map of registered dams No. 1 to No. 4 (PDF)
- https://www.pref.niigata.lg.jp/uploaded/attachment/48362.pdf
- Niigata Prefecture: Bannai River Sabo Park
- https://www.pref.niigata.lg.jp/sec/jouetsu_sabou/bannai-park.html
- JSCE Kanto Branch: Bannai River sabo dams and Hikagesawa ground sills
- https://www.jsce.or.jp/branch/kanto/04_isan/h29/h29_8.html
Last verified: 2026.09.24
