知床半島における河川の自然環境の保全とダム問題に関する意見

概要

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We discuss different perspectives relating to stream-environment conservation on the Shiretoko Peninsula, Japan, given the large number of dams in this area. Over 330 dams have been installed on this peninsula, of which most are check dams. Many species of Salmonidae, which are the primary fish of this peninsula, are anadromous. Dams have narrowed fish habitats in streams by blocking their migration routes, which could also have a devastating impact on terrestrial ecosystems. One reason for the large number of check dams in this area is that housing developments are concentrated on narrow flat areas, which are hazardous with regard to debris flows and flooding. This has undermined the conservation of stream environments. Information on the distribution of residential developments and infrastructure is required for rehabilitation and conservation of the stream environments on the peninsula; in addition, data on the characteristics of the natural environment must be collected and organized. The prevention of disasters caused by debris flows must be reconsidered, including a review of dams and land use based on the above information. Fishways are not a sufficient solution. It is important to develop novel ways to control debris flows and to facilitate fish passages that will avoid the complete blockage of entire channel sections.
2005-12-25