What Are Bannai River No. 7 and No. 8 Sabo Dams?
Bannai River No. 7 and No. 8 Sabo Dams (万内川七号及び八号堰堤, Bannaigawa Nanagō oyobi Hachigō Entei) are a pair of sabo dams built side by side around 1926 on the Bannai River in Nishinoya, Myoko City, Niigata Prefecture, and registered together as a single Registered Tangible Cultural Property on March 18, 2003.
Sabo dams are check dams that trap sediment in mountain streams. These two were built as neighbors at the same time and are counted as one site. Both are gravity dams of stone and concrete. According to the Agency for Cultural Affairs database, No. 7 is 42 meters long at the crest and 3.0 meters high, and No. 8 is 50 meters long and 3.2 meters high. Revetments line both banks downstream, a secondary dam stands in front of No. 7, and the pair was remodeled around 1933.
A Japan Society of Civil Engineers nomination document gives the length of No. 7 as 47 meters and records the remodeling around 1933 for No. 8 only. The figures here follow the agency's database, but the sources do differ.
Why They Were Registered
Most of the registered Bannai dams were listed as contributing to the historic landscape of the country. Bannai River No. 7 and No. 8 Sabo Dams were registered under a different criterion: structures that would not be easy to reproduce.
The reason, according to the Agency for Cultural Affairs, is that irrigation water is drawn off from the right bank just upstream of No. 7. The pair are sabo dams that also serve as an intake weir for the rice paddies below, a combination the agency describes as rare. For Nishinoya, which lost most of its fields to the 1902 debris flow, it meant flood defense and a water supply for farming from the same structure.
What to Look For
Start by getting the layout straight. The numbers rise going upstream, so No. 8 is the upper dam and No. 7 the lower one. Below No. 8, a stone apron and stone revetments run on to No. 7, and below No. 7 there is a further secondary dam. From the top the water drops over No. 8, crosses the apron, falls over No. 7, and drops once more at the secondary dam.
The intake is on the right bank just above No. 7. Taking water from the pool the dam backs up is a very direct link between these dams and the paddies of the village.
From Viewpoint 2 on the prefecture's explorer map, No. 7 and No. 8 appear stacked in steps above No. 6. At 50 meters, No. 8 has the longest crest of all the registered dams, and its span across the valley is clear even from the viewpoint.
How to Visit
Bannai River No. 7 and No. 8 Sabo Dams lie just upstream of No. 6. Take in all three from Viewpoint 2 first, then continue along the path for a closer look at the apron between the pair and the intake area above No. 7.
Bannai River No. 7 and No. 8 Sabo Dams 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.
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Q&A
- Why are Bannai River No. 7 and No. 8 Sabo Dams registered as one property?
- The two dams were built next to each other at the same time as a single scheme, so they are counted as one site. They were registered together on March 18, 2003.
- What is special about Bannai River No. 7 and No. 8 Sabo Dams?
- Irrigation water is drawn from the right bank just upstream of No. 7, so the pair work as both sabo dams and an intake weir. That rare combination is why they were registered as structures that would not be easy to reproduce.
- When were Bannai River No. 7 and No. 8 Sabo Dams built?
- Around 1926, with remodeling around 1933, as part of the sabo project Niigata Prefecture began on the Bannai River in 1921.
- Can I visit Bannai River No. 7 and No. 8 Sabo Dams, and is there a fee?
- Yes. They are outdoors and can be seen freely from the path and from Viewpoint 2. Bannai River Sabo Park is open from April to November and there is no charge.
- Where is Bannai River No. 7 and No. 8 Sabo Dams?
- Bannai River No. Directions to Bannai River Sabo Park are on the Bannai River Sabo Facilities page.
Basic Information
| Name | Bannai River No. 7 and No. 8 Sabo Dams (万内川七号及び八号堰堤) |
|---|---|
| Location | Nishinoya, Myoko City, Niigata Prefecture |
| Designation | Registered Tangible Cultural Property (Structure), Registration No. 15-0149 |
| Year Designated | Registered 2003/3/18 (Heisei 15) |
| Quantity | 1 site (2 dams) |
| Dimensions | No. 7: crest length 42 meters, height 3.0 meters / No. 8: crest length 50 meters, height 3.2 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: 万内川七号及び八号堰堤
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00003216
- 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
- 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
