Impact of stem size on turbulence and sediment resuspension under unidirectional flow

Abstract

Laboratory experiments examined the impact of model vegetation on turbulence and resuspension. The turbulent kinetic energy increased with increasing velocity and increasing solid volume fraction, but did not depend on stem diameter. The vegetation-generated turbulence dominated the total turbulence inside canopies. For the same sediment size, the critical turbulent kinetic energy at which resuspension was initiated was the same for both vegetated and bare beds, which resulted in a critical velocity that decreased with increasing solid volume fraction. Both the critical turbulence and critical velocity for resuspension had no dependence on stem diameter. However, for denser canopies and/or a canopy of smaller stem size, a greater energy slope is required to initiate resuspension. This study provides a way to predict the onset of resuspension in regions with vegetation, an important threshold for sediment transport and landscape evolution.