Tsūjun Bridge

Tsūjun Bridge (通潤橋 -kyō) is an aqueduct in Yamato, Kumamoto, Japan. It is an arch bridge completed in 1854 and is 84.0m long. The arch spans 27.3m. It is the largest stone aqueduct in Japan.^[1]

Tsujun Bridge in 2007.Water flows from left to right

Tsūjun Bridge discharges water and accumulated silt in May 2007.

The Japanese Agency for Cultural Affairs has designated the bridge an National Treasure.^[1]^[2]

History and technology

This bridge exemplifies the high level of stone bridge technology in existence at the time of its construction. Yasunosuke Futa (1801–1873), who was the head of the then Yabe village, planned it and, after obtaining funding, succeeded in building the bridge in 1854 with the help of the group of 41 stone technicians and many farmers. Its purpose was to let water flow into a higher area (Shiroito Plateau) for farming. After placing wooden frames, stones were placed on the frames and three stone aqueducts were made. After that, the wooden frames were removed. Because the aqueducts were lower than the upper part of the waterway by 6 metres (20 ft), a reversed siphon mechanism works when water flows through the aqueducts. The stone aqueducts were made watertight with mortar. The bridge was completed in 1854.

Because the aqueduct is lower than the upstream and downstream waterways, sand and mud may accumulate in the aqueduct. To clean the accumulated dirt, the bridge is able to occasionally release water (and dirt) into the river below. This is mostly done in the farmers' off-season.^[3]

References

^ ^a ^b 通潤橋（熊本県）. 文化財の紹介 (in Japanese). Agency for Cultural Affairs. Archived from the original on 10 September 2012. Retrieved 17 September 2011.
^ "文化審議会の答申（国宝・重要文化財（建造物）の指定）" [Report of the Council for Cultural Affairs (designation of national treasures and important cultural properties (structures))] (PDF) (in Chinese).
^ Handbook of international bridge engineering. 11 October 2013. p. 1058. ISBN 9781439810309. OCLC 859154927.