Study on Effect of Characteristics of River Boundaries on Sediment Transport Process

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The key to the study of an alluvial process is to elucidate interactions between flow properties, sediment movements and bed or channel configurations. For this reason, any physical model of sediment transport is required to describe reasonably the non-equilibrium state of an alluvial process. From this point of view, the sediment model has been recently reinvestigated on the basis of knowledge accumulated on the mechanism of sediment motion. In this research, firstly, effect of the characteristics of the boundaries on the flow structure is investigated. Particularly, the special attention is paid to the velocity profile and turbulent structure over a rough permeable bed. A gravel bed is characterized by small relative submergence and steep slope, the flow resistance and the sediment transport behaviours on which are somehow different from those on a sand bed.Many informations collected for alluvial channels are on longer valid for gravel-bed rivers. The flow resistance and the sediment-transport mechanics are closely related to the velocity profile which represents the turbulent structure. Thus in this paper, the flow structure is discussed with particular reference to the effects of large roughness and high permeability of a bed, using carefully measured velocity-profile date. Secondary, Particularly, importance is attached to unified treatment of bed material load, taking into account the transition from bed load motion to suspension both through incipient motion and transport process, and a physical model for description of non-equilibrium situation is proposed by applying a stochastic approach. Further in order to predict the scouring process of river banks, formation of armor coat, incipience of debris flow, etc., the effects of channel boundaries such as side slope, sand mixtures and permeable bed on sediment transport process are discussed.