Background and future problems on influences of dam structure as introduction of the special feature

Abstract

The experimental flood from Glen Canyon Dam in spring 1996 and Columbia basin program to bring back salmon in the 1980s initiate a new era of dam management in the United States. Conservation and improvement of river environment was included in the purpose statement of the new River Law in Japan, which was revised in 1997. Reservoir dams, erosion control dams and other dam structures are thought to have considerable effects on the structure and function of river ecosystem, but very few studies in Japan have demonstratively elucidated such effects. In order to provide present knowledge on influences of dam structure, studies in Japan and other countries were reviewed from the viewpoints of hydraulics, geomorphology, riparian forest dynamics, water quality, benthic animals, and fish life history. We believe that the idea of Adaptive Management will be useful as a future management strategy within a limited knowledge of dam influences.