EXPERIMENTAL STUDY ON BED SHEAR STRESS AND SEDIMENT TRANSPORT IN A MEANDERING LABORATORY CHANNEL

1 INTRODUCTION River erosion is a complex phenomenon. The rate of bank retreat is determined by flow, bed topography, sediment transport, bank properties, and water quality. Prediction of future river planform changes and the knowledge of river erosion and river meandering are required for land use planning in alluvial river valleys and determining locations for bridges and hydraulic structures. The control of riverbank erosion requires prediction of flow and bed features in a meanderin…

EXPERIMENTAL STUDY ON BED SHEAR STRESS AND SEDIMENT TRANSPORT IN A MEANDERING LABORATORY CHANNEL

An experimental study was carried out to investigate bed shear stress of a flow boundary layer with meandering features and sediment transport in a meandering channel. By measuring the shear stress distribution with hot-film sensors, the stability of the fluid-bed interface and the characteristics of the bed features were investigated experimentally in a laboratory model for free-surface flow over an erodible bed. The experimental results are presented in two parts. First, experimental observations of meander evolution due to inhomogeneous distribution of boundary layer meander features are qualitatively described in terms of the shear stress distribution. Second, an empirical relation is proposed for the shear stress distribution measured with WTG-50 hotfilmanemometer at the wavy iron bed. The sediment transport rate measured in the meandering channel in a laboratory flume was used to evaluate and compare the sediment transport formulae of Shield (1936), Meyer-Peter and Mller (1948), Einstein (1950), and Bagnold (1966). The sedimentation rates computed using these formulae were found to be generally higher than those observed in the laboratory. However, the Einstein formula yields these rates closest to the measured ones but with an over-prediction of 64.5% in general. Using the experimental observations, empirical formulae were also developed for predicting the sediment transport rate and the meander planforms for a specific condition.