Shohoji River Kitasawa No. 1 Stone Dam

About the Kitasawa No. 1 Stone Dam

The Shohoji River Kitasawa No. 1 Stone Dam (正法寺川北沢第一号石堰堤, Shōhōjigawa Kitasawa) is a stone erosion-control dam built in 1922 on the Kitasawa branch of the Shohoji River in Shimo-Oginoto, Tendo City, Yamagata Prefecture, and was listed as a Registered Tangible Cultural Property in 2005.

The dams on the Kitasawa are numbered from the top of the ravine downward, and this is where the count begins. The Agency for Cultural Affairs describes the Shohoji River Kitasawa No. 1 Stone Dam as standing at the very head of the Shohoji River. It is a gravity dam of stone, 14 metres along the crest and 4.6 metres high, with a stone apron on its downstream side.

Why It Was Registered

What sets the No. 1 dam apart is the way it was laid: dressed stone, no mortar, in level courses. Japanese masons call the dry technique Karazumi and the coursed pattern Nunozumi. The Agency for Cultural Affairs singles out this combination as rare among erosion-control dams, and Yamagata Prefecture puts the dam first in its list of representative structures on the river.

The Shohoji River Kitasawa No. 1 Stone Dam was registered as a structure that would be difficult to reproduce. The upstream face is battered at 2 bu and the downstream face at 3 bu (two and three parts horizontal to ten vertical), a gravity profile that holds back water and sediment by weight alone, with nothing but the fit of the stones to keep it together.

What to Look For

Stand to one side of the Shohoji River Kitasawa No. 1 Stone Dam and follow the courses across the face. Because the stones are laid in level rows, each course keeps an even height, a very different look from the net-like diagonal joints of the mortared dams further down the valley.

Then look below the crest. The apron (mizutataki) is a paved floor of stone that takes the impact of water spilling over the dam so that it cannot scour out the streambed and undermine the structure. Dam and apron work as a pair.

About 55 metres downstream sits the No. 1-Ko dam, and from there the Kitasawa dams follow one another at intervals of a few dozen metres.

Visiting the Kitasawa No. 1 Stone Dam

The Shohoji River Kitasawa No. 1 Stone Dam is an open-air river structure with no admission fee or opening hours. The face of the dam is best seen from the downstream bank; do not walk along the crest or climb down into the stream when the water is up. The No. 1-Ko dam is about 55 metres downstream.

Directions to the valley and safety notes are on the page for the Shohoji River Erosion Control Facilities.