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

(1)通过对水生-无脊椎动物组合的对比分析，观察到了水生-无脊椎动物组合与河床脆弱性的关系，并用摩阻速度与临界摩阻速度之比来评价河床的脆性。(2)河流侵蚀治理工作的进展影响了某一水生-无脊椎动物群落的生活方式，导致了该河流水生-无脊椎动物群落的变化，但多元方差分析表明，透水沙坝对水生-无脊椎动物群落的影响不大。(3)在建造防渗坝的河床中，由于单调的水深和流速，滞流区占主导地位，因此出现了极端的沉积和随后的凋落物分解。因此，人们认为溪流水质不仅取决于溪流中现有的植被，还取决于河床岩石。(4)水生昆虫倾向于在建造不透水的沙波坝的溪流中漂流寻找替代栖息地，但这种趋势在建造了透水的沙波坝的溪流中并不明显。

(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.