透過型砂防ダムの渓流生態系保全機能に関する実証的研究

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(1) A pattern of aquatic-invertebrate assemblage in relation to the fragility of stream bed due to the of erosion control work in the stream was observed by the comparative analysis of aquatic-invertebrate assemblage with the fragility of the stream beds estimated by the ratio friction speed to critical friction velocity. (2) While the progress of erosion control work in a stream affects life styles of an certain species of aquatic-invertebrate assemblage, inducing the variation of aquatic-invertebrate assemblage of the stream, it was statistically supported by multivariate analysis of variance that permeable sabo dam influences hardly aquatic-invertebrate assemblage. (3) In a stream bed where impermeable sabo dams are constructed, extreme deposit and subsequent decomposition of litters were observed because stagnant zones dominate due to monotonic water depth and flow velocity. Therefore, it was suggested that stream water quality depends on existing vegetations as well as bed rocks in the stream. (4) Aquatic insects tend to drift to seek for alternative habitats in a stream where impermeable sabo dams are constructed, but this tendancy is not remarkable in the permeable sabo dam constructed stream.