What the Kamakurazawa River No. 5 Sabo Dam Is
The Kamakurazawa River No. 5 Sabo Dam is a cyclopean concrete check dam faced in stone on the Kamakurazawa River in Yoshizato, Minamiuonuma City, Niigata Prefecture, completed in 1929 and entered on the national register as a Registered Tangible Cultural Property structure on 4 August 2015.
It is 31 meters long and 3.0 meters high, and stands about 80 meters above the No. 2 Sabo Dam, one of the wider gaps in the sequence. The Agency for Cultural Affairs records it as the lowest of three dams built above a bend in the main channel. Where a valley turns, the current presses against the outer bank and gathers speed, so the engineers placed dams immediately upstream of the bend to settle the flow before it got there.
The body is cyclopean concrete with a stone face laid on the diagonal. That is the reverse of the arrangement recorded downstream at the No. 2 Sabo Dam, where masonry encloses a concrete fill. Two dams a year apart on the same stream are classified under different structural types, which says something about how quickly the technology was moving.
Among Niigata's First Nationally Subsidised Sabo Works
Registration came under the criterion of contributing to the historic landscape of the country, recommended on 13 March 2015 and entered on 4 August that year as registration number 15-0414.
The national database describes this dam as one of those built in the earliest nationally subsidised erosion-control project in Niigata Prefecture after the Mannaigawa works in Myoko City. Under that funding arrangement the central government met part of the cost of sabo work carried out by a prefecture, which is how serious protection reached torrents far from the major rivers. That the Kamakurazawa River was chosen so soon after Mannaigawa indicates how early the degradation of this particular valley had been recognised as a problem.
Minamiuonuma City records that the stream flooded almost every year, and that the works begun in 1927 were directed by Dr. Masao Akagi, the leading figure in modern Japanese sabo engineering. They produced the first stream-conservation channel works in the prefecture, and the Kamakurazawa River No. 5 Sabo Dam belongs to the third year of that effort.
One of Three Above the Bend
Start by noticing which way the river runs. Below this dam the main channel changes direction. On the outside of a bend the bank erodes and the water accelerates, and this stretch answers that with three dams in succession, dropping the gradient of the bed in stages before the flow reaches the turn. The Kamakurazawa River No. 5 Sabo Dam is the lowest of the three; the No. 6 and No. 8 dams follow above it.
The facing stones are set on the diagonal in the bond called tanizumi, so the joints cross at an angle rather than running level. At 3.0 meters the dam is not tall enough to loom, but the same pattern continues across all 31 meters, and the eye takes it in as a long raking stripe rather than as a wall.
Cyclopean concrete, the material of the body, is concrete poured around large fragments of broken stone. It saves cement, which was the practical consideration on a site where everything had to be carried up the valley.
Visiting the Kamakurazawa River No. 5 Sabo Dam
This is a working outdoor structure with no interior. Viewing is from the bank, without charge, with no reception and no restriction on photography.
The 80 meters separating it from the No. 2 Sabo Dam below make this the longest gap in the lower half of the sequence, and the bend in between can hide the dam from view, so watch for it as you go. From here to the No. 6 Sabo Dam is only about 40 meters, and above that point the dams come thick and fast.
Stay out of the streambed; water collects on the outside of a bend when the level rises. Snow closes the valley in winter, so plan for roughly May to November. Directions and the parking situation are set out on the Kamakurazawa River Sabo Facilities page.
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Q&A
- Can the Kamakurazawa River No. 5 Sabo Dam be visited?
- Yes, from the bank at any time and free of charge. There is no car park and no footpath, and the streambed is not a safe place to walk.
- Why is the Kamakurazawa River No. 5 Sabo Dam linked to Niigata's earliest subsidised sabo works?
- Because the Kamakurazawa River project followed the Mannaigawa works in Myoko City as one of the first in the prefecture to receive national funding. The national database states this directly.
- How is the Kamakurazawa River No. 5 Sabo Dam built?
- As a cyclopean concrete dam with a diagonally laid stone face, 31 meters long and 3.0 meters high. It was completed in 1929 and registered as a Registered Tangible Cultural Property (structure) under number 15-0414.
- What kind of site does the Kamakurazawa River No. 5 Sabo Dam occupy?
- It is the lowest of three dams placed above a bend in the main channel, with the No. 6 and No. 8 dams continuing upstream from it.
- Who directed the work that produced the Kamakurazawa River No. 5 Sabo Dam?
- According to Minamiuonuma City, the sabo works carried out on this stream between 1927 and 1935 were guided by Dr. Masao Akagi, the leading figure in modern Japanese erosion-control engineering.
Basic Information
| Name | Kamakurazawa River No. 5 Sabo Dam (鎌倉沢川第五号堰堤) |
|---|---|
| Location | Yoshizato, Minamiuonuma City, Niigata Prefecture |
| Designation | Registered Tangible Cultural Property (Structure) |
| Year Designated | Registered 2015/8/4 (Heisei 27) |
| Quantity | 1 site |
| Dimensions | 31 meters long, 3.0 meters high |
| Owner | Niigata Prefecture |
| Public Access | Working outdoor structure; exterior visible from the bank at any time, no interior access |
References
- National Cultural Properties Database: Kamakurazawa River No. 5 Sabo Dam (Agency for Cultural Affairs)
- https://kunishitei.bunka.go.jp/heritage/detail/101/00010579
- Sabo Facilities on the Kamakurazawa River Entered on the National Register (Niigata Prefecture, Minamiuonuma Regional Promotion Bureau)
- https://www.pref.niigata.lg.jp/sec/minamiuonuma_seibi/1356827806289.html
- Registered Cultural Properties of Minamiuonuma City (Minamiuonuma City Board of Education)
- https://www.city.minamiuonuma.niigata.jp/docs/890.html
Last verified: 2026.09.12
