Seventy-eight square metres of sediment control
The Kamisaibara Power Station Ikego Channel Settling Basin is a water structure of 1930 in the Kawamuki district of Kamisaibara, Kagamino, Okayama Prefecture, and it was listed as a Registered Tangible Cultural Property on 29 November 2006. It lies about 40 metres below the Ikego River intake weir and takes the sand out of the water before it travels any further.
At 78 square metres it is the smallest of the nine registered structures at this station. The side walls are built as mortared masonry, and the floor is laid to fall towards the west, so that whatever settles works its way across to a sand gate in the west wall and can be flushed out. Everything about the basin is arranged around that one movement.
Along the east wall, the side facing the hill, a reinforced concrete slab is cantilevered out over the water. Its purpose is defensive: soil and stones washing down the slope land on the slab instead of in the channel. It is a small piece of engineering that has quietly prevented a great deal of maintenance for close to a century.
Why the basin was registered
Registration number 33-0144 belongs to the Kamisaibara Power Station Ikego Channel Settling Basin. It was one of nine structures of the station accepted on 29 November 2006 under the criterion that they contribute to the historic landscape of the country.
The register was set up in 1996 to cover buildings and works that continue in use. It asks an owner to notify the authorities before major alteration instead of demanding that nothing change, and a Registered Tangible Cultural Property therefore usually keeps its original role. Okayama Prefecture lists all nine of these structures as facilities in current service.
Registering something this modest says something about how the group was assessed. The value was not found in any single showpiece but in the survival of a complete working set: three intake weirs, two settling basins on the tributary channels, a confluence basin, a head tank, stone retaining walls and a powerhouse, all of 1930 and all still connected. Remove the small parts and the sequence stops making sense.
What to look at
Mortared masonry is the technique to notice in the side walls. Stones are bedded in mortar rather than fitted dry, which gives a watertight wall without the cost of a full concrete section. In 1930, in a valley where cement had to be carried in, that saving was real, and the choice reappears throughout the group wherever a wall did not have to carry heavy load.
Then look at the slope of the floor. It is easy to miss because it is gentle, and it is the whole design. A level floor would need men with shovels; a floor that falls to a gate needs an operator to open a gate.
Finally, stand back and take in the relationship between the Kamisaibara Power Station Ikego Channel Settling Basin and the weir 40 metres upstream. The short distance is deliberate. Sand dropped close to the intake can be returned to the same stream through the sand gate, whereas sand carried further would have to be moved a long way back or carted out.
Visiting
The basin is a working component of a generating scheme, with no admission charge, no ticket office and no published opening hours. It stands inside the operator's fence beside a maintenance track.
Okayama Prefecture asks anyone wishing to see the facilities to arrange it beforehand with the Tsuyama Power Office of Chugoku Electric Power, on 0868-27-0275. Ask about photography on the same call.
Kawamuki lies in the northern part of Kamisaibara, in country reached from National Route 179 between Tsuyama and Ningyo Pass. Using public transport, take the JR Kishin Line to Tsuyama Station or Inno-sho Station, then the Chutetsu Hokubu Bus service towards Okutsu Onsen and Ishigoshi; timetables are published by Kagamino town. The final approach is on forest lanes without footways, and snow closes them in midwinter.
- 📍 Plan Your Visit to Okayama
- Find tours, activities & transport passes near Kamisaibara Power Station Ikego Channel Settling Basin
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Q&A
- What does the Kamisaibara Power Station Ikego Channel Settling Basin do?
- It slows the water in the Ikego channel so that sand settles out, then discharges the deposit through a sand gate in the west wall. Clean water goes on towards the station.
- How big is the Kamisaibara Power Station Ikego Channel Settling Basin?
- It covers 78 square metres, which makes it the smallest of the nine registered structures belonging to this station.
- What is the concrete slab along the east side for?
- It is cantilevered out from the wall on the hill side to catch soil and stones washing off the slope, keeping them out of the water.
- How far is it from the Ikego River intake weir?
- About 40 metres downstream, which is close enough for flushed sand to return to the same stream.
- Can I visit it?
- Not without arrangement. It sits inside the operator's fence. Okayama Prefecture gives 0868-27-0275, the Tsuyama Power Office of Chugoku Electric Power, as the contact for viewing the facilities.
Basic Information
| Name | Kamisaibara Power Station Ikego Channel Settling Basin |
|---|---|
| Location | Kawamuki, Kamisaibara, Kagamino-cho, Tomata-gun, Okayama Prefecture |
| Designation | Registered Tangible Cultural Property (structure) |
| Year Designated | Registered 1930 structure on 2006-11-29 |
| Quantity | 1 site |
| Dimensions | Reinforced concrete, area 78 square metres; mortared masonry side walls, cantilevered slab on the east wall, sand gate in the west wall |
| Owner | Chugoku Electric Power Co., Inc. |
| Public Access | Operating facility. No public entry; viewing of the plant by prior arrangement with the Tsuyama Power Office, 0868-27-0275 |
References
- National Cultural Properties Database, Agency for Cultural Affairs: Kamisaibara Power Station Ikego Channel Settling Basin
- https://kunishitei.bunka.go.jp/heritage/detail/101/00006066
- Cultural Heritage Online, Agency for Cultural Affairs: Kamisaibara Power Station Ikego Channel Settling Basin
- https://online.bunka.go.jp/heritages/detail/143331
- Okayama Prefecture, Cultural Properties Division: Registered Cultural Properties in Okayama Prefecture
- https://www.pref.okayama.jp/page/detail-50777.html
- Okayama Prefecture: Kamisaibara Power Station Facilities (PDF)
- https://www.pref.okayama.jp/uploaded/attachment/260992.pdf
- Chugoku Electric Power Co., Inc.: List of hydroelectric power stations
- https://www.energia.co.jp/energy/general/water/water_all.html
- Kagamino Town: Route buses and public transport
- https://www.town.kagamino.lg.jp/soshiki/22/2132.html
Last verified: 2026.09.08