<p>Turbulence is a fundamental aspect of the natural river system, significantly influencing sediment transport processes, variations in channel morphology, and changes in ecological habitats. Understanding the complex interplay between turbulence and sediment movement in the channel bed is crucial for predicting bed morphology. Using a bimodal sediment bed in a flume setup, velocity fluctuations were measured with a three-dimensional Acoustic Doppler Velocimeter (ADV) to estimate time-averaged velocities, Reynolds shear stress, turbulence intensities, and turbulent kinetic energy. The findings highlighted the significant variations in turbulence parameters in both longitudinal and transverse directions of the channel. Longitudinally, turbulence parameters decreased downstream due to sediment sorting and downstream finning effects. Transversely, wall shear stress and secondary current formations led to notable spatial variability. Additionally, the bimodality index showed both longitudinal and lateral variation, and mutually interacting with local turbulence characteristics, which was also discussed. The study also examines the formation of current crescents, revealing their dependence on flow conditions, turbulence effects, and sediment characteristics. These insights enhance the understanding of the river morphology changes due to sediment properties and provide valuable pieces of information for the development of more accurate sediment models and effective river management strategies.</p>