EXPERIMENTAL STUDY ON THE CAPTURE OF FINE MATERIALS CONSIDERING SUBSURFACE WATER FLOW AT GRAVEL-BARS

Abstract

 In the sediment reproduction to the river downstream of the dam, fine materials including turbidity are trapped in the gravel-bar in the river channel, and there is a problem that they cannot reach the sea. In this study, the hydraulic experiments were conducted to grasp the trapping mechanism of fine sediment in the turbid flow at the gravel-bar. As a result, the gravel-bar with a large grain size ratio and a small porosity in the gravel bar had higher fraction of fine materials. It was also found that the fraction of fine materials increased in proportion to length of the gravel-bar and the hydraulic gradient, and that the turbulent structure and clogging of the sub-surface flow affected the fraction of fine materials.