Forty-One Metres of Concrete
Onabe Sabo Dam is an erosion-control dam completed in 1957 on the lower Ozo River, a tributary east of the Tedori, at Seto and Kinameshin in Hakusan City, Ishikawa Prefecture, listed on 23 February 2012 as a Registered Tangible Cultural Property. Built in concrete, it runs 60.7 metres across and stands 41.0 metres high, among the largest sabo dams in Japan.
Of the fifteen sabo structures on Hakusan listed that day, thirteen stand in the Jinnosuke Valley and one in the Yanagidani ravine, all of them masonry dams from the Taisho and early Showa years. Onabe Sabo Dam is the only postwar structure among them, and the only one owned by the national government rather than the prefecture. In scale and in character it belongs to a different chapter.
Designed by Three-Dimensional Stress Analysis
What earned Onabe Sabo Dam its listing is how it was designed. It was the first sabo dam in Japan designed using three-dimensional stress analysis, and it is valued as a record of the design and construction practice of its moment. The engineer responsible was Professor Ryuichi Endo of Kyoto University.
Among three-dimensional sabo dams in Japan, its height of 41.0 metres is the greatest. Its sediment storage capacity reaches 2.3 million cubic metres, another figure near the top of the national list. Because water passing over the crest threatened to hammer and erode the bedrock below the wing sections, an apron was laid to protect the rock.
Registration is a notification-based form of protection, separate from the permit-based designation system. The dam qualified as a structure contributing to the historic landscape of the country.
Why the Ozo River
The Ozo flows east of the Tedori and joins it lower down, and Onabe Sabo Dam sits in its lower reaches. Where the dams of the Jinnosuke and Yanagidani valleys were built high up to hold failing headwaters in place, this one works further down the system, catching the sediment that gets past everything above it.
Sabo work on Hakusan began in 1910, when Ishikawa Prefecture confronted the state of the Yanagidani ravine, and became a national project in 1927. In 1934 a flood on the Tedori killed 97 people. Onabe Sabo Dam was finished 23 years after that flood, at the point where the programme moved from hand-laid stone in the headwaters to concrete engineering on the scale of a whole basin.
Visiting
Onabe Sabo Dam is a working structure with no opening hours and no admission fee. It cannot be walked on, no interpretive panels or viewing facilities have been provided, and the ground around it is managed by the transport ministry.
The Kanazawa River and National Highway Office keeps a monitoring camera on the dam and publishes the images as part of its live information service for Hakusan sabo. Rain gauges, water level gauges and seismometers watch the upper Tedori basin around the clock for floods and moving sediment. If you want to see the dam without going there, that feed is the reliable way.
The Hakusan Sabo Science Museum at Hakumine sets out the wider story. It opens from 9 a.m. to 5 p.m., admission is free, and it closes on Thursdays, or the following day when a Thursday is a public holiday, and from 29 December to 3 January.
Q&A
- When was Onabe Sabo Dam built?
- It was completed in 1957, the only postwar structure among the fifteen Hakusan sabo facilities listed together in 2012.
- How big is Onabe Sabo Dam?
- It is a concrete dam 60.7 metres long and 41.0 metres high, the tallest three-dimensional sabo dam in Japan.
- Why was Onabe Sabo Dam listed as heritage?
- Because it was the first sabo dam in Japan designed using three-dimensional stress analysis, making it a record of the design and construction practice of its time.
- What is the apron at Onabe Sabo Dam for?
- Water spilling over the crest threatened to hammer and erode the bedrock below the wing sections, so an apron was laid to protect the rock.
- Can I visit Onabe Sabo Dam?
- It is a working structure with no visitor facilities and cannot be walked on. The transport ministry publishes images from a monitoring camera on the dam as part of its live information service.
Basic Information
| Name | Onabe Sabo Dam |
|---|---|
| Location | Hakumine, Hakusan City, Ishikawa Prefecture |
| Designation | Registered Tangible Cultural Property (structure) |
| Year Designated | Registered 2012/02/23 (Heisei 24) |
| Quantity | 1 structure |
| Dimensions | 60.7 metres long, 41.0 metres high |
| Owner | Ishikawa Prefecture |
| Public Access | Working structure in the open; no visitor facilities |
References
- Agency for Cultural Affairs, National Cultural Properties Database
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00009159
- Kanazawa River and National Highway Office: Fifteen Facilities Listed as Registered Tangible Cultural Properties
- https://www.hrr.mlit.go.jp/kanazawa/hakusansabo/03history/touroku.html
- Kanazawa River and National Highway Office: History of the Hakusan Sabo Project
- https://www.hrr.mlit.go.jp/kanazawa/hakusansabo/03history/history01.html
- Kanazawa River and National Highway Office: Civil Engineering Heritage Certification
- https://www.hrr.mlit.go.jp/kanazawa/hakusansabo/03history/isan01.html
- Ishikawa Prefecture: Traffic Restrictions during the Hakusan Climbing Season
- https://www.pref.ishikawa.lg.jp/hakusan/tozaninf/peak2.html
- Ishikawa Prefecture: Mandatory Submission of Climbing Plans for Hakusan
- https://www.pref.ishikawa.lg.jp/bousai/bousai_g/hakusan_kazan/jorei.html
Last verified: 2026.09.19