Abstract
This review paper provides useful information for understanding studies on the ‘riverbed environment’ of the upper and middle reaches of rivers. Firstly, as the basis for evaluating the characteristics of a riverbed, the physical properties of bed material (classification and distribution of grain size, porosity, specific gravity etc.) are discussed so as to find ways to apply these physical properties to ecological studies. It is proposed that sediment population analysis provides a useful framework for discussing the habitat functions of riverbed. Secondly, we summarize the results of studies on flow resistance, flow structure in the roughness layer, riverbed forms, and sediment transport in a mixed bed. We point out the importance of focusing on bed forms and sediment sorting, as a cause of the heterogeneity of the riverbed environment. Thirdly, index parameters and classification of the physical condition of a riverbed are discussed including properties that an appropriate index should possess. Finally, future issues and expected actions are proposed based on the review of sediment hydraulics and fluvial geomorphology.
