A study on the formation of bed forms in rivers and coastal waters

Abstract

In this study, mechanisms of bed form generation are investigated by linear instability analysis. The analysis suggests that the slope factor and the perturbed bed shear stress are the two key parameters under bed-load dominant sediment transport conditions. A bed-load transport model and the associated slope factor are validated and strongly supported by laboratory data. A slip velocity model (SV-model) based on constant eddy viscosity and a GM-model based on linearly varying eddy viscosity are proposed to predict the perturbed bed stress. The proper correlation between eddy viscosity and slip factor, neglected in most previous studies, is considered in the SV-model. The GM-model predicts more realistic near-bed velocity profiles. The effects of wind waves are taken into account for the first time in the present study. The models are applied to predict dunes in rivers and sand waves in coastal waters with reasonable success.