Arakawa Eighth Dam

What the Arakawa Eighth Dam Is

The Arakawa Eighth Dam (荒川第八堰堤, Arakawa Dai-hachi Entei) is a gravity-type concrete sabo dam built in 1952 on the Arakawa River at Yasumiba, 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 60 meters long and 12 meters high, and Fukushima City lists the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) as the owner.

Among the 15 registered Arakawa River Sabo Dams, it stands about 400 meters above the Arakawa Seventh Dam and about 1,200 meters below the Arakawa Third Dam. It was registered as a Registered Tangible Cultural Property in 2008 under number 07-0091.

The Top Step of a Three-Dam Staircase

The Agency for Cultural Affairs does not describe the Arakawa Eighth Dam as a stand-alone structure. It presents it as one of three dams built in sequence with Kawakami First Dam and the Arakawa Seventh Dam downstream. Those three were completed in 1946, 1951 and 1952; about 200 meters separate Kawakami First from the Seventh, and about 400 meters the Seventh from the Eighth. All three fit into roughly 600 meters of river.

The Agency names three aims for the set: to ease the gradient of the streambed, to stabilize the banks, and to help vegetation return. When dams follow one another down a steep channel, sediment fills in behind each one and the bed becomes a series of steps. The current slows, the banks erode less, and slopes that had been stripped bare can green over again.

The Eighth is the top step. What matters here is less the work of one dam than the layout of all three.

How the Arakawa Eighth Dam Is Built

The dam follows the group's standard section: an upstream face sloping 1 to 0.45 and a near-vertical downstream face of 1 to 0.2, finished in stone.

At 12 meters it matches the height of the Arakawa Seventh Dam, though at 60 meters it is a little shorter than the Seventh at 69 meters. Kawakami First Dam, the lowest of the three, is 9.0 meters high, 3 meters less than the two above it. Of the ten main-river structures in the group, only the Arakawa Fifth Dam and the Fourth Groundsill are younger than the Eighth.

Seeing the Arakawa Eighth Dam

The Arakawa Eighth Dam is a working sabo structure. Viewing is free from the surrounding ground; you cannot walk on the dam or enter the riverbed.

It makes most sense when approached in order, climbing from Kawakami First Dam past the Seventh. Three dams stepping up the valley within about 600 meters is something you only feel on foot. Since the Agency credits the set with helping the greenery recover, look at the plant cover on both banks as you go.

The dam is in the hills above Tsuchiyu Onsen, and paths narrow upstream. Wear sturdy shoes and stay out of the valley after rain. Directions are on the Arakawa River Sabo Dams page.