渓流河川における河床砂礫の混合特性と階段状河床形の形状特性

抄録

Recently, studies on step-pool systems in mountain streams become increasing for the concerns with environmental conservation. However, there cannot be found any study to elucidate roles of heterogeneous property (grain size distributions) of bed materials for the step-pool formations. This paper presents that 1) the grain size distributions of the bed surface materials sampled in the upper Ibi River show the type of Talbot distribution, which is known to give the closest packing;2) comparative experiments of step-pool formations using the heterogeneous bed materials with Talbot type distribution and non Talbot type distribution, resulted in that stable and well developed step-pools were formed in the case of the former materials, but any step-pools were not found in the caseusing the latter materials;3) evaluating equations for a wave length and a wave height of a step-pool were newly derived by considering the effect of the grain size distribution of Talbot, and they agreed with the modes of the experimental data fairly well.