The Sagami Dam is a multi-purpose dam on the main stream Sagami River in Sagamihara, Kanagawa Prefecture on the island of Honshū, Japan. The potential of the Sagami River valley for hydroelectric power development began to be developed in the 1930s, with the growth of population in the Shonan region, and the expansion of industry and e…The Sagami Dam is a multi-purpose dam on the main stream Sagami River in Sagamihara, Kanagawa Prefecture on the island of Honshū, Japan. The potential of the Sagami River valley for hydroelectric power development began to be developed in the 1930s, with the growth of population in the Shonan region, and the expansion of industry and electrical consumption in the Yokohama-Kanagawa industrial belt. Plans for a dam on the Sagami River were submitted to the Home Ministry in 1935, but approval was delayed in favor of other projects. Instead, the Kanagawa Prefectural Assembly passed the necessary regulations and secured a special budget to begin work in 1938.