Increasing flood control capacity: Case studies from Japan

Many dams in Japan were constructed after World War II to regulate floods, generate hydropower, and supply water for agricultural and urban use, supporting a period of high economic growth. Therefore, many of them have now been in operation for more than 50 years, and as the dam facilities have deteriorated, the functions that these structures must provide have also changed. It is difficult to construct new dams because of a shortage of appropriate sites, relocation, environmental and financial problems. Thus, many redevelopment projects have been carried out in Japan to improve the functions of existing dams. This article describes these issues, as well as two examples of Japan’s redevelopment projects for increasing flood control capacity: the Tsuruda dam; and, the Kanogawa dam, which are the largest redevelopment projects of their type in Japan.