Experimental study on effects of geometric distortion upon suspended sediments in bending channels

- Experiments were conducted in distorted physical bending channel models.
- Geometric distortion gives influence on suspended sediment transport.
- Riverbed deformation is not impacted unless distortion ratio is less than 4.
- Distortion impacts are magnified if the width-depth ratio is larger than 25.
- Deviation in riverbed deformation is larger in bending channel than straight channel.

Different geometries of bending channels are set up without distortion and with distortion ratios of 2, 4, 6, 8 and 10 in order to study its influence on bed deformation induced by suspended sediment transport in these channels. Experiment results show that the kinematics of suspended sediment is inversely proportional to the distortion ratio of the physical model, but proportional to the width-depth ratio and curvature ratio. The similar bed deformation to that of the non-distorted model is only observed in the distorted models with distortion ratios of not more than 4 and width-depth ratios of not less than 6.3. It is recommended that the geometric distortion ratio be less than 4 in order to meet the similarity requirements of river bed deformation in bending channels. With the same distortion ratio, deviation of bed deformation was observed more in the bending reaches than in the straight ones and more with a fixed convex bank than with a mobile convex bank. The geometric distortion affects the river bed deformation in the model, i.e., the amount of deposition and erosion and the profiles of river bed deformation in longitude and transverse directions.