A study of sediment transport in two-stage meandering channel

An investigation of the flow characteristics and sediment transport processes has been carried out in a two-stage meandering channel. Three phases of experiments have been conducted with various floodplain roughnesses. The dimensions of the flume are 13m long and 2.4m wide with a fixed valley slope of 11500. The meandering main channel has a sinuosity of 1.384 with top width of 0.4m. In each phase of the experiment, hydraulic data pertaining to stage-discharge, bed topography and sediment transport rate were measured at various overbank flow depths. Several flow depths were chosen to measure the three-dimensional velocities by means of Laser Doppler Anemometer and the morphological bedforms were recorded using the Photogrammetric technique. The boundary shear stresses were also measured by means of a Preston Tube and Vane Indicator. The experimental results showed that the presence of the energy losses due to momentum exchange and turbulence, bedforms roughness and floodplain roughness induced additional flow resistance to the main channel flow, particularly for shallow overbank flows. The combination of these losses affected a significant reduction in velocity and boundary shear stress in the main channel which, subsequently led to the reduction of sediment discharge at low relative depth for most tested cases. The reduction was more pronounced when the floodplain roughness increased. The examination of the three-dimensional velocity indicated that the formation of bedforms in the main channel is significantly affected by the flow structures, especially the secondary flow. A new method for predicting velocity and sediment transport rate has been introduced based on the two-dimensional equation (Spooner's) coupled with the self-calibrated empirical transport formula. The proposed method gave accurate prediction for depthaveraged velocity and sediment transport rate for two-stage meandering channel.