A Forest Railway Tunnel at Koyagauchi
The Former Taisho Forest Railway Koyagauchi Tunnel (旧大正林道木屋ヶ内トンネル) is a concrete tunnel of a forest railway, built in 1944 at Koyagauchi, Shimanto Town, Takaoka District, Kochi Prefecture, and registered as a Registered Tangible Cultural Property (structure) on March 7, 2008 (Agency for Cultural Affairs).
The Agency for Cultural Affairs records reinforced concrete, partly plain concrete, 138 metres long and 2.5 metres wide, registration number 39-0247, owned by Shimanto Town.
Cutting Through a River Bend
According to Shimanto Town, state forests along the Yusuhara River were logged heavily from the Meiji to the Showa era. In 1911 the Miura timber company of Susaki laid the first forest tramway in the Shimanto basin; the forestry office bought it in 1925, set up a timber yard at Tanono (now Taisho, Shimanto Town) and extended the line inland, creating the Taisho line along the Yusuhara River to Shimotsui.
According to Shimanto Town, the Former Taisho Forest Railway Koyagauchi Tunnel was dug through a small hill on a river terrace on the right bank of the Yusuhara River. Where the river loops sharply, it cuts across the neck of the bend, shortening the route while keeping a gentle curve. Every day locomotives hauled trucks loaded with timber through it.
Value as a Registered Cultural Property
The Former Taisho Forest Railway Koyagauchi Tunnel was registered as a structure contributing to the historic landscape of the country. The Agency for Cultural Affairs identifies it as the longest tunnel on the former Taisho forest railway.
Shimanto Town presents the Former Taisho Forest Railway Koyagauchi Tunnel as a structure that conveys the history of modern forestry and timber haulage in the Shimanto basin, and as a component of the Cultural Landscape of the Shimanto River Basin (Taisho Oku-Shimanto Area).
What to Look For
The Agency for Cultural Affairs describes the Former Taisho Forest Railway Koyagauchi Tunnel as a straight bore about 100 metres south of Koyagauchi Bridge, its portals simple horseshoe openings with a keystone motif at the crown, finished in mortar.
Shimanto Town notes that after the railway closed the sleepers and rails were removed, and the Former Taisho Forest Railway Koyagauchi Tunnel was paved, lit and fitted with a water main to serve local residents as a town road.
Visiting
The Former Taisho Forest Railway Koyagauchi Tunnel is in use as a town road, so watch for traffic and respect local residents (Shimanto Town). It is at Koyagauchi, Shimanto Town. See the group page Former Taisho Forest Railway (Shimanto) for all four structures.
- 📍 Plan Your Visit to Kochi
- Find tours, activities & transport passes near Former Taisho Forest Railway Koyagauchi Tunnel
- [ Katsurahama Beach & Kochi Castle Ryoma Tour ]
Q&A
- When was it built?
- In 1944, according to the Agency for Cultural Affairs.
- How long is it?
- 138 metres in the Agency for Cultural Affairs record, the longest tunnel on the Taisho line.
- What are the portals like?
- Simple horseshoe openings with a keystone motif, finished in mortar (Agency for Cultural Affairs).
- How is it used today?
- The rails were removed and it was paved as a town road (Shimanto Town).
- When was the Former Taisho Forest Railway Koyagauchi Tunnel registered?
- On March 7, 2008.
Basic Information
| Name | Former Taisho Forest Railway Koyagauchi Tunnel (旧大正林道木屋ヶ内トンネル) |
|---|---|
| Location | Koyagauchi, Shimanto Town, Takaoka District, Kochi Prefecture |
| Designation | Registered Tangible Cultural Property (Structure) |
| Year Designated | Registered 2008/03/07 (Heisei 20) |
| Quantity | 1 structure |
| Dimensions | Reinforced concrete, partly plain concrete, length 138 metres, width 2.5 metres |
| Owner | Shimanto Town |
| Public Access | Passable as a town road |
References
- Former Taisho Forest Railway Koyagauchi Tunnel (Database of National Cultural Properties, Agency for Cultural Affairs)
- https://kunishitei.bunka.go.jp/heritage/detail/101/00006948
- Cultural Landscape of the Shimanto River Basin, Taisho Oku-Shimanto Area 1 (Shimanto Town)
- https://www.town.shimanto.lg.jp/life/detail.php?hdnKey=1284
- Cultural Landscape of the Shimanto River Basin, Taisho Oku-Shimanto Area 2 (Shimanto Town)
- https://www.town.shimanto.lg.jp/life/detail.php?hdnKey=1283
Last verified: 2026.10.11
