Shohoji River Minamizawa No. 8 Stone Dam

Shobojigawa Minamisawa Dam No. 8

Dam No. 8 is the only dry-laid structure in the group. Built without mortar, it resists the water by the interlock of stone against stone alone, a different craft from the mortared dams around it.

In 1913 a great flood tore through the Shobojigawa valley. In response, Yamagata Prefecture spent the years from 1922 to 1927 building masonry check dams through the ravines above Shimo-Oginoto in Tendo City. The stream drains through the Kuratsugawa into the Mogami River.

About seventy-five metres below No. 7. Alone in the group, it is built dry, without mortar, as a gravity dam. Like the others it uses rhyolitic welded tuff, laid at a gentle five-bu batter on both faces and one-wari-six-bu on the overflow sides.

Why It Matters

The Shobojigawa scheme sets sixteen dams along the north branch, three along the Tanuki ravine and ten along the south branch, together with wire-gabion current-control works. No single dam is large; instead they are strung from upstream to down, catching sediment stage by stage.

This dam is laid dry, karazumi, without mortar. It holds back the water by the weight and interlock of the stones alone, which demands careful selection and fitting and drains freely through the wall.

In 2005 the Shobojigawa erosion-control facilities were placed on the national register of tangible cultural properties. The listing cites their contribution to the historical landscape of the country, recognising a modern civil-engineering work as heritage that shapes the character of a place.

Seeing It Today

The dam sits along a mountain stream, not at a developed sightseeing spot. Watch your footing, and stay away when the water is high. Look closely at the face of each set stone and the finish of the overflow lip, and the density of hand labour from before mechanisation comes into view.

The dam measures 21 metres along its crest and stands 3.0 metres high. It belongs to the Minamisawa branch and was completed in 1926.