What Is the Inari River Second Sabo Dam?
The Inari River Second Sabo Dam (稲荷川第二砂防堰堤, Inarigawa Daini Sabō Entei) is a concrete gravity erosion-control dam built in 1920 on the Inari River in the Kaerusawa and Nakasuzu area of Nikko City, Tochigi Prefecture, and registered in 2002 as a Registered Tangible Cultural Property (Structure) of Japan, with effect from 21 August. It is 40 meters long and 7.0 meters high and belongs to the national government (Ministry of Land, Infrastructure, Transport and Tourism).
Of the seven registered Inari River Sabo Dams, this is the oldest. It sits 110 meters upstream of the Fourth Dam and 84 meters downstream of the Third, in the middle of a short run where three dams follow one another closely. Its registration number is 09-0056, and it was registered under the criterion of serving as a model of design.
Built after the First Dam Failed
The first dam completed under the national erosion-control program on the Inari, the First Dam, was finished in the summer of 1919 and was carried away by a debris flow during a storm on 15 September that same year. It had been built as Karazumi, stacked stone without mortar. A photograph published by the Nikko Sabo Office shows a huge boulder that the same flood rolled down to the area near the future Second Dam.
The Inari River Second Sabo Dam was the engineers' answer. The Agency for Cultural Affairs notes that it was built as Nerizumi, with mortared joints, precisely because the dry-stone First Dam had been lost. According to the Nikko Sabo Office it was completed on 2 August 1920 as the first sabo dam on the river to use rubble concrete, and it held firm in a major flood that same year. That result encouraged the expansion of the whole Inari River program.
So although it carries the number two, the Second Dam is the oldest surviving dam of the national program on the Inari.
The Prototype of the Kaba Type
The Agency for Cultural Affairs describes the Inari River Second Sabo Dam as the oldest example of the features shared by the dams of this project: mortared masonry, and a broad trapezoidal Spillway notch (spillway notch) whose corners are rounded off. It also names the designer, Home Ministry engineer Kaba Makoto (蒲孚). The notch shape that the Japan Society of Civil Engineers calls the "Kaba type" starts here.
Eight rectangular drain holes pierce the dam body. They let water held behind the dam seep through gradually, easing the pressure on the structure. On the right bank, a 40-meter stretch of mortared stone revetment still guards the riverbank beside the dam's wing. According to the JSCE, the downstream Sub-dam (sub-dam) was demolished and rebuilt in 1994, and the dam was repaired in 2006.
What to Look for at the Inari River Second Sabo Dam
The Inari River Second Sabo Dam is an outdoor erosion-control facility with no admission fee. You see it from the path along the river; climbing onto the structure is not allowed.
The thing to study is the outline of the notch. Stand facing the dam from downstream and you can see that the shoulders of the cut where the water pours over are rounded rather than sharp. From the same spot you can count the eight square drain holes in the face and follow the stone revetment along the right bank. The low wall in front is the 1994 sub-dam, not part of the original structure.
The Fourth Dam downstream and the Third Dam upstream are each a few minutes' walk away, so you can compare three dams from 1920 and 1921 in one short stretch. Directions to the dams are on the Inari River Sabo Dams page.
- 📍 Plan Your Visit to Tochigi
- Find tours, activities & transport passes near Inari River Second Sabo Dam
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Q&A
- When was the Inari River Second Sabo Dam built?
- In 1920. The Nikko Sabo Office gives a completion date of 2 August 1920, which makes it the oldest of the seven registered Inari River Sabo Dams.
- Why is the Inari River Second Sabo Dam older than any "first" dam on the river?
- The First Dam was destroyed by a debris flow on 15 September 1919, shortly after it was finished. The Second Dam was the first to be rebuilt in mortared masonry in response, and it is the oldest that survives.
- Who designed the Inari River Second Sabo Dam?
- The Agency for Cultural Affairs credits Kaba Makoto, an engineer of the Home Ministry. His broad, round-shouldered trapezoidal spillway notch later became known as the "Kaba type."
- What are the holes and the stone wall at the Inari River Second Sabo Dam?
- The eight rectangular openings are drain holes that let water behind the dam pass through. The stone wall on the right bank is a 40-meter mortared revetment that protects the bank.
- Can I visit the Inari River Second Sabo Dam, and is there a fee?
- Yes. You can view it from the riverside path at no charge. It is a working erosion-control dam, so you cannot climb onto it, and you should keep away from the stream after rain.
Basic Information
| Name | Inari River Second Sabo Dam (稲荷川第二砂防堰堤) |
|---|---|
| Location | Aza Kaerusawa and Nakasuzu, Oaza Nikko, Nikko City, Tochigi Prefecture |
| Designation | Registered Tangible Cultural Property (Structure) |
| Year Designated | Registered in 2002 |
| Quantity | 1 structure |
| Dimensions | 40 meters long, 7.0 meters high (concrete gravity dam with right-bank revetment) |
| Owner | Government of Japan (Ministry of Land, Infrastructure, Transport and Tourism) |
| Public Access | Outdoor erosion-control facility; exterior viewable from the riverside path (no fee) |
References
- Agency for Cultural Affairs, Database of National Cultural Properties: Inari River Second Sabo Dam
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00002882
- Cultural Heritage Online: Inari River Second Sabo Dam
- https://online.bunka.go.jp/heritages/detail/168192
- MLIT Kanto Regional Development Bureau, Nikko Sabo Office: History of the Registered Sabo Dams (Japanese)
- https://www.ktr.mlit.go.jp/nikko/nikko00038.html
- Japan Society of Civil Engineers, Kanto Branch: Sabo Dams of the Inari River Basin, Nikko (Japanese)
- https://www.jsce.or.jp/branch/kanto/04_isan/h26/h26_3.html
- Tochigi Prefecture Cultural Properties: Inari River Second Sabo Dam (Japanese)
- https://bunkazai.pref.tochigi.lg.jp/cultural/%E3%80%90%E7%A8%B2%E8%8D%B7%E5%B7%9D%E7%AC%AC%E4%BA%8C%E7%A0%82%E9%98%B2%E5%A0%B0%E5%A0%A4%E3%80%91/
Last verified: 2026.10.01
