EXPERIMENTAL AND 2D NUMERICAL MODELLING OF MORPHOLOGY AND BANK EROSION IN MEANDERING CHANNELS OF DIFFERENT SINUOSITY

Abstract

River Bank erosion is a serious problem in meandering rivers which continuously evolve due to erosion-deposition phenomena, adjusting their geometric characteristics such as sinuosity, curvature radius and deflection angle. Through experimental and numerical analysis, the objective of this study is to identify the channel morphological changes including the locations where bank erosion could be high. In addition, the suitability of different arrangement of impermeable groynes for mitigating bank erosion is examined. Experiments were conducted in two different sine-generated meandering channels of varying sinuosity and curvature under the erodible bed and bank composed of non-cohesive sediment. From the experiments, it was observed that the higher sinuosity channel exhibit more complexity in bed morphology compared to the lower sinuosity channel, which showed distinct pool-bar patterns. The location and the extent of bank erosion also differed according to the sinuosity. Bank erosion was higher in lower sinuosity channel, requiring high level of bank protection. The 2D numerical simulation reasonably reproduced the phenomena observed in the experiments. Simulations showed that groynes placed beginning from downstream of the outer bank apex are more effective in shifting high bed shear stress zone away from the outer banks for low sinuosity channel, whereas in higher sinuosity channel, groynes placed exactly from the apex work slightly better.