What Are the Hikagesawa Upper Reach Ground Sills?
The Hikagesawa Upper Reach Ground Sills (日影沢上流域床固工, Hikagesawa Jōryūiki Tokogatamekō) are a group of stone ground sills built in the late Taisho era (the early 1920s) and extended around 1937 on the upper reach of the Hikagesawa stream in Nishinoya, Myoko City, Niigata Prefecture, and were registered together as a Registered Tangible Cultural Property on July 1, 2003.
The Agency for Cultural Affairs database lists five stone ground sills running 31 meters, with one more on a side stream. According to its commentary, the five sills, from 6 meters to 21 meters long and from 1.5 meters to 3 meters high, stand on a slope of about 40%, and a tributary joins from the right bank. The group counts as one site.
A ground sill is a low wall across a stream bed that fixes its level and prevents erosion. These are the uppermost of the registered Hikagesawa structures.
Why They Were Registered
They were registered as structures contributing to the historic landscape of the country. The Agency for Cultural Affairs notes that the Hikagesawa Upper Reach Ground Sills are finely built of cut stone and effectively stabilize the ground of a steep slope.
A gradient of about 40% is steeper still than the roughly 30% of the middle reach. Here, cut stone laid as Tanizumi holds the foot of a slope prone to collapse, making this the group placed in the hardest conditions on the Hikagesawa.
What to Look For
Look at how the stone is worked. As the agency specifically notes, the Hikagesawa Upper Reach Ground Sills use cut stone, shaped before laying. Compared with the split river stones of the Bannai River dams, the faces and joints are more even, a more labor-intensive finish.
The stones are laid in tanizumi, set on the diagonal so that neighbors lean into one another, with the direction alternating from course to course to form a zigzag. Bannai River No. 12 Sabo Dam is also known for fine tanizumi, so the same technique was used on both dams and sills within one project.
Packing five sills and a side-stream sill into just 31 meters probably serves to keep the drop each wall has to hold small on a 40% slope.
How to Visit
The Hikagesawa Upper Reach Ground Sills are the highest of the Hikagesawa structures, beyond the middle reach.
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 the Hikagesawa Upper Reach Ground Sills; 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 Upper Reach Ground Sills
- [ Sado Island & Echigo-Yuzawa Ski Resort Tours ]
Q&A
- What are the Hikagesawa Upper Reach Ground Sills?
- A group of stone ground sills on the upper Hikagesawa: five sills from 6 meters to 21 meters long and 1.5 meters to 3 meters high on a slope of about 40%, plus one on a side stream.
- Why are the Hikagesawa Upper Reach Ground Sills a Registered Tangible Cultural Property?
- They were registered on July 1, 2003, as structures contributing to the historic landscape. They are finely built of cut stone and stabilize the ground of a steep slope.
- When were the Hikagesawa Upper Reach Ground Sills built?
- In the late Taisho era (the early 1920s), with an extension around 1937.
- What is special about the masonry of the Hikagesawa Upper Reach Ground Sills?
- Dressed cut stones are laid in tanizumi, set diagonally so they lean into one another, which gives the walls an alternating zigzag pattern.
- Can I visit the Hikagesawa Upper Reach Ground Sills?
- No visitor path could be confirmed. The prefecture says there is not even a maintenance road up the Hikagesawa and that one to the upper reach is only under consideration. Do not try to reach them; use the photographs on the prefecture's website instead.
Basic Information
| Name | Hikagesawa Upper Reach Ground Sills (日影沢上流域床固工) |
|---|---|
| Location | Nishinoya, Myoko City, Niigata Prefecture |
| Designation | Registered Tangible Cultural Property (Structure), Registration No. 15-0159 |
| Year Designated | Registered 2003/7/1 (Heisei 15) |
| Quantity | 1 site (5 stone ground sills, plus 1 on a side stream) |
| Dimensions | 31 meters long overall (individual sills from 6 meters to 21 meters long, from 1.5 meters to 3 meters high) |
| 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: 日影沢上流域床固工
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00003398
- Cultural Heritage Online: Hikagesawa Upper Reach Ground Sills
- https://bunka.nii.ac.jp/heritages/detail/139168
- Niigata Prefecture: Hikagesawa stone ground sills (Registered Tangible Cultural Properties)
- https://www.pref.niigata.lg.jp/sec/jouetsu_sabou/bunkazai-hikagesawa.html
- Niigata Prefecture: Repairs to the Hikagesawa stone ground sills
- https://www.pref.niigata.lg.jp/sec/jouetsu_sabou/renewal-hikagesawa19th.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
