Abstract
When the sediment supply from the upstream region is suppressed, the bed-surface composed of graded material becomes coarsened as self-adjustment of fluvial bed so as to make the bed-load discharge on it equivalent to the supplied load through non-equilibrium process of bed-load transport for each grain size. When no sediment is supplied, the bed is “armored”; while for finite but suppressed sediment supply the bed is “paved”. Under equilibrium states, no sediment is transported on armored bed, but some on paved bed. Although these two coarsened beds have different properties, both processes can be reasonably described without any difference by a model constituted by pick-up rate and step length for each grain size. Several properties empirically induced from laboratory-experiments and field-observations are discussed based on the present analytical model.
