Yanagihara suikō, Cultural sluice in Shimo-yakiri, Japan

Yanagihara suikō is a disused brick sluice on the Sakagawa in Shimo-yakiri, Matsudo, Chiba. Built in 1904, it has a four-arch structure measuring 17 m across the river and 13 m along it, with brick and stone arches on stone piers. It was designed by engineer Inoue Jirō, born 1873.

The sluice was built during Japan's industrial modernization period and later designated as a Cultural Property of Japan. This recognition honors its role in advancing modern water control technology during that era.

The name Yanagihara suikō combines the locality name with the word for a water gate. The structure was built by the Sakagawa Ordinary Water Users' Association, a body of local farmers and landowners, to control flooding along the Sakagawa in the Edogawa basin. It is now preserved as a cultural property rather than used for water control.

The sluice stands at Shimo-yakiri 1397 in Matsudo, Chiba Prefecture, about 20 minutes on foot from Yagiri Station on the Hokuso Line. By bus, take the Keisei bus from the west exit of Matsudo Station (JR Joban Line, Keisei Matsudo Line) toward Ichikawa Station and get off at Kuriyama, then walk about 15 minutes. Some walking routes nearby involve long slopes.

The site holds three separate heritage designations at once: Cultural Property of Japan, Heritage of Industrial Modernization, and Civil Engineering Heritage. This triple recognition is relatively uncommon and reflects the structure's importance across different aspects of Japanese heritage.