Arakawa Second Dam

What the Arakawa Second Dam Is

The Arakawa Second Dam (荒川第二堰堤, Arakawa Dai-ni Entei) is a gravity-type concrete sabo dam built in 1938 and extended in 1941 on the Arakawa River at Aburabata, Tsuchiyu Onsen-cho, in Fukushima City, Fukushima Prefecture, and registered as a Registered Tangible Cultural Property (structure) of Japan on March 7, 2008. It is 54 meters long and 13 meters high, with a Sub-dam (sub-dam) on its downstream side. Fukushima City lists the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) as the owner.

It belongs to the 15 registered Arakawa River Sabo Dams and stands about 1,600 meters upstream of the Arakawa Sixth Dam, directly above the hot-spring town of Tsuchiyu Onsen. Its registration number is 07-0088.

A Dam Placed Above a Spa Town

Tsuchiyu Onsen is a cluster of inns and bathhouses in the valley where the Higashi Karasu River joins the Arakawa. The Agency for Cultural Affairs states the purpose of the Arakawa Second Dam plainly: it protects the hot-spring town from sediment disasters.

National sabo work on the Arakawa began in 1936, and this was the second dam after the Arakawa First Dam of 1937. In the year it was completed, 1938, a debris flow struck the Higashi Karasu River, and MLIT's Fukushima office lists that disaster among the events that led the government to widen its sabo program. The Agency's record also notes an extension in 1941 but does not say which part was added.

The Widest Crest on the River

According to the Agency, the Arakawa Second Dam has the widest crest of any modern sabo dam on the Arakawa, a sturdy build in its words. The crest is the flat top of the dam, and a thicker crest means a heavier body better able to absorb the blows of boulders carried down in a flood.

The slopes differ slightly from its neighbors. Most of the registered dams have an upstream face of 1 to 0.45, while this one is 1 to 0.4. The downstream face follows the common 1 to 0.2, standing nearly vertical, and the surface is faced with stone.

At 13 meters, it is the second tallest of the ten registered structures on the main river, after the 15-meter Arakawa Third Dam. The sub-dam downstream breaks the fall of water spilling over the main dam so it does not scour the riverbed below.

Seeing the Arakawa Second Dam

The Arakawa Second Dam is a working sabo structure. There is no fee; you view it from nearby and cannot walk on the dam or go down to the riverbed.

The point of interest is its relationship to the town. The streets of Tsuchiyu Onsen begin just downstream, which makes it easy to see what this dam is guarding. From the downstream side, the thick crest reads as a level band across the valley, with the sub-dam in front forming a two-step profile.

The dam lies within walking distance of the Tsuchiyu Onsen bus stop. Keep well back from the banks after rain, when the water rises fast. Directions to the area are on the Arakawa River Sabo Dams page.