What Is Hikagesawa No. 1 Ground Sill?
Hikagesawa No. 1 Ground Sill (日影沢一号床固工, Hikagesawa Ichigō Tokogatamekō) is a stone ground sill built in the late Taisho era (the early 1920s) on the Hikagesawa stream in Nishinoya, Myoko City, Niigata Prefecture, and was registered as a Registered Tangible Cultural Property on July 1, 2003.
A ground sill is a low wall built across a stream bed to fix its level and stop the current from cutting it down. Hikagesawa No. 1 Ground Sill is 30 meters long at the crest and 5.0 meters high, with both faces at a batter of 1:0.3 and a narrow spillway notch only 3.4 meters wide. Its left-bank wing is extended to fit the shape of the valley.
Sources place it slightly differently. The Agency for Cultural Affairs database says it stands where the Hikagesawa joins the Bannai River, while the prefecture's page puts it about 300 meters upstream of the confluence.
Why It Was Registered
It was registered as a structure contributing to the historic landscape of the country. The Agency for Cultural Affairs describes Hikagesawa No. 1 Ground Sill as the lowest and largest structure in the Hikagesawa group, playing the central role in the whole system.
The Hikagesawa sills work as a flight of low stone steps that hold the bed of a steep stream in place. If the bottom step gave way, every sill above it would lose its footing. The outsized scale of No. 1 reflects the weight of that position.
What to Look For
The first thing to notice is the asymmetry. Only the left-bank wing runs long past the notch, because the length of the masonry was set by the cross-section of the valley rather than by a symmetrical drawing.
At 3.4 meters, the notch is less than a quarter as wide as the notches of 15 meters on Bannai River dams No. 6 and No. 14. The sill is as high as Bannai River No. 1 Sabo Dam, at 5.0 meters, but it gathers the flow into a narrow slot, a proportion suited to the small Hikagesawa.
With both faces battered at 1:0.3, the trapezoidal section is a gravity design that resists earth and water pressure by sheer weight of stone. It is the largest stone wall among the registered Hikagesawa structures.
How to Visit
Hikagesawa No. 1 Ground Sill lies just inside the Hikagesawa from its junction with the Bannai River.
The prefecture says there is no road up the Hikagesawa even for maintenance, which makes it hard for its own staff to check the structures for damage, and it has been considering building one as far as the upper reach. No visitor path or signage could be confirmed. The ravine is steep, so do not try to scramble up to Hikagesawa No. 1 Ground Sill; the photographs on the prefecture's website are the practical way to see it. Directions to Bannai River Sabo Park, and viewing conditions for the dams on the Bannai itself, are covered on the Bannai River Sabo Facilities page.
- 📍 Plan Your Visit to Niigata
- Find tours, activities & transport passes near Hikagesawa No. 1 Ground Sill
- [ Sado Island & Echigo-Yuzawa Ski Resort Tours ]
Q&A
- What is Hikagesawa No. 1 Ground Sill?
- It is a stone ground sill built in the late Taisho era (the early 1920s) on the Hikagesawa stream to fix the stream bed and stop erosion. At 30 meters long and 5.0 meters high, it is the lowest and largest of the Hikagesawa sills.
- Why is Hikagesawa No. 1 Ground Sill a Registered Tangible Cultural Property?
- It was registered on July 1, 2003, as a structure contributing to the historic landscape. As the lowest and largest structure in the group, it anchors the whole system of Hikagesawa sills.
- What are the features of Hikagesawa No. 1 Ground Sill?
- A trapezoidal section with both faces battered at 1:0.3, a narrow 3.4-meter notch, and a wing extended only on the left bank to fit the valley.
- Can I visit Hikagesawa No. 1 Ground Sill?
- It stands outdoors, but no visitor path could be confirmed. The prefecture says there is not even a maintenance road up the Hikagesawa, so do not try to reach it; use the photographs on the prefecture's website instead.
- Where is Hikagesawa No. 1 Ground Sill?
- In Nishinoya, Myoko, near where the Hikagesawa joins the Bannai River. The agency's database places it at the confluence; the prefecture puts it about 300 meters upstream.
Basic Information
| Name | Hikagesawa No. 1 Ground Sill (日影沢一号床固工) |
|---|---|
| Location | Nishinoya, Myoko City, Niigata Prefecture |
| Designation | Registered Tangible Cultural Property (Structure), Registration No. 15-0157 |
| Year Designated | Registered 2003/7/1 (Heisei 15) |
| Quantity | 1 structure |
| Dimensions | Crest length 30 meters, height 5.0 meters |
| Owner | Niigata Prefecture |
| Public Access | Outdoors, but no visitor route could be confirmed; the prefecture says there is not even a maintenance road up the Hikagesawa |
References
- Agency for Cultural Affairs, Database of National Cultural Properties: 日影沢一号床固工
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00003396
- Cultural Heritage Online: Hikagesawa No. 1 Ground Sill
- https://bunka.nii.ac.jp/heritages/detail/179616
- Niigata Prefecture: Hikagesawa stone ground sills (Registered Tangible Cultural Properties)
- https://www.pref.niigata.lg.jp/sec/jouetsu_sabou/bunkazai-hikagesawa.html
- JSCE Kanto Branch: Bannai River sabo dams and Hikagesawa ground sills
- https://www.jsce.or.jp/branch/kanto/04_isan/h29/h29_8.html
Last verified: 2026.09.24
