Results obtained from both of flume data and theories suggest that equilibrium bed slope in flow over an erodible bed are determined uniquely by sediment discharge rate when the movements of sediment particles are laminar and thus no suspended transportation take place. This means that the static friction force is dominant in debris flow and that sediment concentration is determined by shear stress balance on the bed surface as seen in our previous studies. On the other hand, if part of sediment particles in debris flow body is transported in suspension, sediment concentration will be larger and the equilibrium bed slope will decrease. These facts are supported by Egashira et al.'s flume data and others' experimental data.
The present study discusses experimentally an influence of flow scales on an equilibrium bed slope and flow structure, based on experimental data and emphasizes that the equilibrium bed slope decreases with increasing of flow scale if part of debris flow body is turbulent.