Application of Entrainment Velocity Concept for Evaluation of River Morphology: A Numerical Model Study

Abstract

Conventionally, fine sediment transport is evaluated in terms of advection-diffusion equation of suspended sediment in which the erosion rate of sediment from the bedload layer plays a significant role. The present study aims to evaluate the riverbed evolution and associated morphological changes in fine sediment dominated Bhairab River of Bangladesh by a depth integrated two-dimensional numerical model. The erosion rate of bed sediment has been evaluated by two approaches. The first approach applies the fall velocity of the sediment particle and equilibrium reference sediment concentration. The other employs the entrainment velocity concept. The results obtained from numerical simulations are verified by the field investigations. The results suggest that the riverbed evolution and morphological changes predicted with the entrainment velocity concept show better agreement with the data obtained from the field investigations.