What Are the Hikagesawa Middle Reach Ground Sills?
The Hikagesawa Middle Reach Ground Sills (日影沢中流域床固工, Hikagesawa Chūryūiki Tokogatamekō) are a series of stone ground sills built in the late Taisho era (the early 1920s) and extended around 1937 on the middle 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 them as 30 stone ground sills running 302 meters, with two more sills on a side stream. Its commentary describes 32 small sills, from 7 meters to 24 meters long and from 1.5 meters to 4.5 meters high, set on a slope of about 30%. The whole group counts as one site.
A ground sill is a low wall across a stream bed that fixes its level and prevents erosion. Thirty-two of them in 302 meters means a line of masonry, on average, less than every 10 meters. The prefecture's page describes the 1937 work as construction, while the agency and the Japan Society of Civil Engineers call it an extension.
Why They Were Registered
They were registered as structures contributing to the historic landscape of the country. The Agency for Cultural Affairs praises the way the Hikagesawa Middle Reach Ground Sills follow one another in curves that settle into the terrain, creating a landscape at one with its natural setting.
Of the Hikagesawa as a whole, the prefecture's introduction highlights 47 ground sills on a steep stream only 1.2 kilometers long, while its repair report says 41 of 49 sills were registered. The middle reach, with 32 sills, is by far the largest cluster.
Sills No. 19 and No. 20 in this reach are built in dry stone (Karazumi), now rare, and after more than 80 years they were badly damaged. A prefectural committee of experts and local residents met four times over fiscal 2005 and 2006 and decided to reinforce them while keeping their dry-stone appearance and passing on the masonry skills. Repairs to the body of No. 19 were completed in 2008 and No. 20 in 2009.
What to Look For
The prefecture's published repair record is a good guide to how these walls are built. Each stone was numbered before removal and returned to its place using photographs. Sound facing stones were left in position, because the sediment packed behind the sills could have pushed them over.
Missing stones were cut from rock on site. Wedges are driven in to split the stone, and, the prefecture notes, only someone trained as a stonemason knows where to set them to get the shape they want. The pieces are dressed with small hammers into pyramid-shaped blocks 0.40 meters wide, 0.25 meters high and 0.35 meters deep, their edges straight without any machine cutting.
A 30% gradient rises 30 meters for every 100 meters of horizontal distance. On that slope, walls from 1.5 meters up to 4.5 meters high follow the bends of the valley in arcs. It is this chain as a whole that the agency describes as one with the landscape.
How to Visit
The Hikagesawa Middle Reach Ground Sills run through the middle of the stream, above Hikagesawa No. 1 Ground Sill.
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 Middle 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.
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Q&A
- What are the Hikagesawa Middle Reach Ground Sills?
- A series of stone ground sills along a 302-meter stretch of the Hikagesawa. According to the Agency for Cultural Affairs, 32 sills from 7 meters to 24 meters long and 1.5 meters to 4.5 meters high are set on a slope of about 30%.
- Why are the Hikagesawa Middle Reach Ground Sills a Registered Tangible Cultural Property?
- They were registered on July 1, 2003, as structures contributing to the historic landscape. The way the stone walls curve up the valley in sequence, fitting the terrain, is cited.
- When were the Hikagesawa Middle Reach Ground Sills built?
- In the late Taisho era (the early 1920s), with an extension around 1937. The prefecture's page describes the 1937 work as construction.
- Have the Hikagesawa Middle Reach Ground Sills been repaired?
- Yes. Dry-stone sills No. 19 and No. 20 were badly damaged, and their bodies were repaired in 2008 and 2009, reinforced while keeping their dry-stone appearance.
- Can I visit the Hikagesawa Middle Reach Ground Sills?
- 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 them; use the photographs on the prefecture's website instead.
Basic Information
| Name | Hikagesawa Middle Reach Ground Sills (日影沢中流域床固工) |
|---|---|
| Location | Nishinoya, Myoko City, Niigata Prefecture |
| Designation | Registered Tangible Cultural Property (Structure), Registration No. 15-0158 |
| Year Designated | Registered 2003/7/1 (Heisei 15) |
| Quantity | 1 site (30 stone ground sills, plus 2 on a side stream) |
| Dimensions | 302 meters long overall (individual sills from 7 meters to 24 meters long, from 1.5 meters to 4.5 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: 日影沢中流域床固工
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00003397
- 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
