What an erosion-control dam is
An erosion-control dam, sabō entei, is built across a mountain valley or torrent to hold back sediment washed down in heavy rain and so protect villages and fields downstream. It is also called a sabo dam. Sediment trapped upstream lowers the gradient of the stream and slows the flow.
From the Meiji era, modern erosion-control works spread across Japan, and many stone and concrete dams were built. The typical layout has a spillway notch cut in the crest, an apron below to take the falling water and a low sub-dam beyond it. The stonework may be mortared, Nerizumi, or dry-laid, Karazumi.
Reading the records and the site
Records give length, height, face slopes and method of laying. The Akatan erosion-control dams in Minamiechizen, Fukui, are nine dams built on the Akatani River from 1900 as the prefecture's first erosion-control project; the uppermost, Ōhira Mizuya-kami, is a dry-laid stone dam 20 metres long and 7.5 metres high on exposed bedrock, built just below a mass of debris and described as a key element of the scheme. The dam groups on the Mannai River in Myoko, Niigata, and the Shohoji River in Tottori also survive as Registered Tangible Cultural Properties.
On site, look for a wall of stone or concrete across the valley with a lowered notch at the centre of its crest, and a flat stone-paved apron and low step downstream.
References
- アカタン砂防大平ミズヤ上堰堤｜国指定文化財等データベース（文化庁）
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00004230
- 万内川四号堰堤｜国指定文化財等データベース（文化庁）
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00003214
- 正法寺川狸沢第一号石堰堤｜国指定文化財等データベース（文化庁）
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00004865
Last verified: 2026.09.27