The First Sabo Dam on the Kamanashi River
The Karasawa Dam (唐沢堰堤) is a sabo erosion-control dam completed in 1950 on the Kamanashi River where it runs between Hakushu-cho, Hokuto City, Yamanashi Prefecture, and Ochiai, Fujimi-machi, Suwa District, Nagano Prefecture, and it was registered as a Registered Tangible Cultural Property on January 15, 2010, under registration number 19-0062.
According to the Agency for Cultural Affairs, it is a gravity dam of concrete, 110 metres long and 12 metres high, with a secondary dam, an apron, revetments, a vertical wall and concrete blocks. The Fujikawa Sabo Office of the Ministry of Land, Infrastructure, Transport and Tourism says construction began in October 1936 and was completed in August 1950; the ministry built it.
Why It Was Registered
The Karasawa Dam was registered as contributing to the historic landscape of the country. The Agency explains that it stands on the upper Kamanashi River in the Fuji River system, faced with stone over a concrete core, and was both the first and the largest sabo dam built on the main Kamanashi River.
The Fujikawa Sabo Office describes the upper Kamanashi as a deep valley with steep cliffs on both banks, scarred by collapses from repeated floods and producing large amounts of sediment. The dam is valued as a record of Showa-era sabo engineering that blends into its setting and creates a fine mountain-stream landscape.
What to Look For
Notice the sequence of main dam, apron and secondary dam. According to the Agency, 17 concrete blocks 3.0 metres square are lined up below the secondary dam to prevent scouring.
The Fujikawa Sabo Office notes that the mortared stones laid when the dam was built can still be seen on its wings and crest. Look for this mortared-stone finish over the concrete body.
Visiting
The Karasawa Dam is a working sabo structure managed by the national government. The Fujikawa Sabo Office has put up warning signs against entry at dams in its area, including the Karasawa dam. Do not climb onto the dam, its wings or the riverbed; view it from a safe distance.
Check with the Fujikawa Sabo Office about viewing and local road conditions.
Q&A
- When was the Karasawa Dam built?
- Construction began in October 1936 and was completed in August 1950.
- When was it registered as a cultural property?
- On January 15, 2010, as registration number 19-0062.
- How big is the Karasawa Dam?
- A concrete gravity dam 110 metres long and 12 metres high.
- Why is the Karasawa Dam important?
- It was the first and largest sabo dam built on the main Kamanashi River and records Showa-era sabo engineering.
- Can I get close to the Karasawa Dam?
- It is a working sabo facility with warning signs against entry; do not climb onto the dam or into the riverbed.
- Patrols and warning signs at sabo facilities (MLIT Fujikawa Sabo Office)
- https://www.ktr.mlit.go.jp/ktr_content/content/000078180.pdf
Basic Information
| Name | Karasawa Dam (唐沢堰堤) |
|---|---|
| Location | Hakushu-cho, Hokuto City, Yamanashi Prefecture / Ochiai, Fujimi-machi, Suwa District, Nagano Prefecture |
| Designation | Registered Tangible Cultural Property (Structure) |
| Year Designated | Registered 2010/1/15 (Heisei 22), registration no. 19-0062 |
| Quantity | 1 structure |
| Dimensions | Concrete gravity dam, length 110 metres, height 12 metres |
| Owner | Ministry of Land, Infrastructure, Transport and Tourism (builder) |
| Public Access | Working sabo facility (no access onto the dam) |
References
- 唐沢堰堤 (Database of National Cultural Properties, Agency for Cultural Affairs)
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00007989
- Registered cultural properties in the Fujikawa Sabo Office area (MLIT)
- https://www.ktr.mlit.go.jp/fujikawa/fujikawa00483.html
- Patrols and warning signs at sabo facilities (MLIT Fujikawa Sabo Office)
- https://www.ktr.mlit.go.jp/ktr_content/content/000078180.pdf
Last verified: 2026.10.04