Shohoji River Minamizawa No. 7 Stone Dam

Shobojigawa Minamisawa Dam No. 7

At a mere 1.5 metres, Dam No. 7 is the lowest in the series. Rather than fight the ground, its builders rounded the corners of the overflow, giving the wall a softer outline.

The Shobojigawa flows out of the hills at Shimo-Oginoto in Tendo City and feeds, by way of the Kuratsugawa, into the Mogami River system. A major flood in 1913 set the prefecture to work: from 1922 to 1927 it laid down a sequence of stone dams along the ravine, and this is one of them.

Some eighty metres below No. 6, and at 1.5 metres the lowest dam in the group. Stone blocks about fifty centimetres square form the apron, and the corners of the overflow are rounded. Its height was held down to sit within the shape of the ground.

Why It Matters

The system divides among three side-ravines, north, Tanuki and south, each carrying its own line of stone dams, with wire-gabion works to blunt the force of the water. The reliance on many small and medium dams rather than a single giant reflects the sabo engineering of the day.

The stones are coursed diagonally, the tanizumi bond, and mortared between, the nerizumi finish, so the body holds together under pressure. Like the other dams here it is built mainly of rhyolitic welded tuff. Both faces are given a 3-bu batter, a nearly upright lean of about one in 3.3.

Intact groups of stone check dams from the 1920s are not common. The 2005 listing set the whole undertaking, a community's long reckoning with landslide and flood, in the frame of cultural heritage.

Seeing It Today

Reaching the dam means walking mountain paths, best avoided after rain or during snowmelt when the stream runs high. Seen from nearby, each block of rhyolitic welded tuff, split and set by hand, still carries the mark of the mason who placed it.

The dam measures 17 metres along its crest and stands 1.5 metres high. It belongs to the Minamisawa branch and was completed in 1926.