河道の変動に関する研究(3) ―流路変動の一次元解析と蛇行流路の形成過程―

Abstract

In the first half of this paper, we describe applicability of the one-dimensional analytical modelof channel process with bank erosion, which was developed in the previous paper2), and a theoreticalconsideration of the stability of channel process by the use of fundamental equations of flow andsedimentation. From comparison between the analytical results and experimental ones undervarious flow and boundary conditions as shown in Table 1, it was concluded that the one-dimensio-nal analytical model is applicable to an uniform and a nonuniform channel widening processwithout meandering pattern by the use of a modified expression of sediment supply due to bankerosion and an assumption on criteria of channel widening at initiation of bed degradation. Theresults of the stability analysis show that the sediment supply due to bank erosion gives no seriousinfluence upon the stability of channel process in the case of the present experiment.In the second half, geometrical and kinematical characteristics of bars in alluvial channels anddevelopment of meandering are discussed on the basis of experimental results. As relationshipsamong width (B), length (LB), height (ZB) and migration velocity (VB) of bars, LB∝B and ZB∝LBwere obtained from those observed here and by other investigators in various alluvial channels andrivers, and VB∝QBLB-2 was derived by the use of the above relations and an expression ofsediment transport rate QB∝BZBVB. Furthermore, relationship on wave length of self-formendmeandering channel to flow discharge was derived in consideration of development and migrationof bars at a given point in the channel and relation between flow and sediment transport rate.