What Is the Yokoyu River No. 3 Dam?
The Yokoyu River No. 3 Dam (横湯川第三号堰堤, Yokoyugawa Dai-sangō Entei) is a gravity-type concrete erosion-control dam built in 1936 directly below the Kurokawa Bridge at the entrance to Shibu Onsen in Yamanouchi Town, Nagano Prefecture, and registered as a Registered Tangible Cultural Property of Japan on October 14, 2021. It is owned by Nagano Prefecture.
It lies about 200 meters above No. 2, third from the bottom of the series. Of the three prefectural dams it was finished first; No. 2 followed downstream a year later and No. 1 the year after that.
At the Gateway to Shibu Onsen
The Agency for Cultural Affairs places the Yokoyu River No. 3 Dam right under the Kurokawa Bridge, the point where Shibu Onsen begins on the river's right bank. The lane of inns and public bathhouses runs upstream from around this bridge.
The agency goes further and calls the dam a foundation for the hot spring town's growth from the Showa era onward. Steadying the riverbed at the foot of the town made the land along the water safe to use. Of the three prefectural dams, this was the spot chosen first.
Concrete Faced with Mortared Stone
The Yokoyu River No. 3 Dam has a concrete body faced with stone set in mortar (Nerizumi), and the agency says it was built to keep the river's course stable. At 40 meters it is the shortest of the three prefectural dams.
Its height is recorded inconsistently. The structure field of the national database gives 3.0 meters, while the descriptive text says 5.0 meters. The basic information below follows the structure field, but which figure is closer to the true measurement has not been confirmed.
Why the Yokoyu River No. 3 Dam Was Registered
The Yokoyu River No. 3 Dam (registration number 20-0593) was registered for its contribution to the historic landscape of the country. Together with the Kurokawa Bridge it frames the approach to the hot spring town, and it has quietly supported Shibu Onsen's development from below.
Seeing the Yokoyu River No. 3 Dam
Because the Yokoyu River No. 3 Dam sits directly beneath the Kurokawa Bridge, the bridge gives you a view straight down onto it. It is an outdoor structure with no admission fee and nothing to go inside. The official photographs show the front from the right bank and the back from the left bank. The Kurokawa Bridge carries road traffic, so watch for cars if you stop to look. No route down to the riverbed is signposted. Directions to Shibu Onsen are on the Yokoyu River Stone Masonry Dams page.
- 📍 Plan Your Visit to Nagano
- Find tours, activities & transport passes near Yokoyu River No. 3 Dam
- [ Matsumoto Castle & Kamikochi Hiking Tours ]
Q&A
- Where is the Yokoyu River No. 3 Dam?
- In the Yokoyu River directly below the Kurokawa Bridge, at the entrance to Shibu Onsen in Yamanouchi, Nagano, about 200 meters above No. 2.
- When was the Yokoyu River No. 3 Dam built?
- In 1936. It was the first of the three prefectural dams (Nos. 1 to 3) to be completed.
- How high is the Yokoyu River No. 3 Dam?
- The national database gives 3.0 meters in its structure field but 5.0 meters in its description, so the figure is uncertain. The dam is 40 meters long.
- What is the link between the Yokoyu River No. 3 Dam and Shibu Onsen?
- It steadied the riverbed at the entrance to the hot spring town, and the Agency for Cultural Affairs credits it as a foundation for the town's growth from the Showa era onward.
- Can I visit the Yokoyu River No. 3 Dam?
- Yes. You can look down on it from the Kurokawa Bridge at no charge. The bridge carries traffic, so take care.
Basic Information
| Name | Yokoyu River No. 3 Dam (Yokoyugawa Dai-sangō Entei) |
|---|---|
| Location | Andai to Kurokawa, Hirao, Yamanouchi Town, Shimotakai District, Nagano Prefecture |
| Designation | Registered Tangible Cultural Property (Structure) |
| Year Designated | 2021 (registered) |
| Quantity | 1 dam |
| Dimensions | Crest length 40 m, height 3.0 m (structure field; the description gives 5.0 m) |
| Owner | Nagano Prefecture |
| Public Access | Outdoor erosion-control structure; viewable from the Kurokawa Bridge and nearby roads (no admission fee) |
References
- Database of National Cultural Properties (Agency for Cultural Affairs): Yokoyu River No. 3 Dam
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00014006
- Cultural Heritage Online: Yokoyu River No. 3 Dam (Japanese)
- https://online.bunka.go.jp/heritages/detail/583496
- Nagano Prefecture Hokushin Construction Office: Design Guidance by Dr. Akagi Masao (PDF, Japanese)
- https://www.pref.nagano.lg.jp/hokuken/documents/akagihakase_sekkei_japanese.pdf
Last verified: 2026.10.01
