Abstract
The main objective of this study is to clarify the evolution process of riverbed where framework is composed of boulders. Such bed consists of three groups of sediment grain sizes: (a) L-particle which cannot move at all even in floods, (b) M-particle which moves as bedload, and (c) S-particle as suspended load. In our recent study, each group was represented by unique size. However, actual riverbed materials have continuous grain size distributions. Then, we investigated how the distributions of M-particle sizes have effects on the structure of riverbed in static equilibrium. As a result, vertical sorting was clearly occurred among L-particles. M-particles are vertically sorted by each diameter. Accumulating knowledge on equilibrium riverbed structure in a series of studies can lead to elucidating the evolution process.
