Application of the Shields diagram for evaluating critical shear stress for vegetated flows

The well-known Shields diagram is developed for unvegetated open channel flows to describe incipient sediment motion by means of critical bed shear stress. Due to difficulties in estimating the bed shear stress in vegetated flows, it is not clear whether the Shields diagram is applicable in the presence of vegetation. By applying the phenomenological theory of turbulence, a new method to evaluate the bed shear stress in vegetated flows is proposed in this study. With this method, the critical bed shear stress subject to vegetated flows is calculated using the published data. The result shows that the calculated critical shear stresses are consistent with the Shields diagram.