Author(s): Makoto Matsushima
Linked Author(s):
Keywords: Water supply; Masonry dam; Bypass tunnel; Seismic retrofit
Abstract: Kobe Water started its water service in 1900. The original water system was planned by Mr. W. K. Burton (1856-1899), a British water engineer; however, the actual design and construction works were done by Japanese civil engineers. Dr. Tojiro Sano designed Kobe Water’s Nunobiki, Karasuhara and Sengari dam s. Among these three dams Nunobiki is the oldest masonry dam in Japan. It was completed in 1900 and had been supplying the world-famous “Kobe Water,” which was supplied to vessels stopping at Kobe Port and to be said to maintain its freshness even if crossing the Equator. Of course, it has been supplied to Kobe citizens without dam cleaning for more than a hundred years. The secret of “Kobe Water” comes from the unique “Clear Water Separation” system. This system is closely linked with the By-pass system. As a result, the Nunobiki dam could prolong its lifespan. The structure of this bypass was designed to mitigate reservoir sedimentation according to some knowledge from the book of Mr. W. K. Burton. The first sediment bypass system was installed in Karasuhara Reservoir, completed in 1905. The Nunobiki system is the second installation in 1908, based on the experience of heavy sedimentation of the Nunobiki dam and the success of Karasuhara Reservoir. In 1995 Kobe City was attacked by the Hanshin -Awaji Great Earthquake. Nunobiki Dam was also damaged and increased leakage from the dam body due to the strong shake. After this disaster, the Dam Research Committee was set up and discussed resiliency upgrade. Following this discussion, it was performed Dam Grouting and Fillet construction as the resiliency upgrade. In this paper, the author will explore the history of the Nunobiki dam, its construction and materials, and will introduce the sediment bypass system and seismic upgrade. After upgrading, Kobe’s Nunobiki Dam was designated “Important Cultural Property” in 2006.
Year: 2020