Author(s): Y. R. Fares

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Abstract: The characteristic changes occurred to the boundary shear stresses in a channel bend at the intersection of flood relief (neck cut-off) channel are investigated. Field measurements for bed topography in a meander loop of a river at the neck cut-off section confirmed the existence of marked changes to that of the riffles/pools pattern found in sinuous meandering channels. Detailed investigation of boundary shear stresses in an idealised rigid bed model is undertaken in order to explain the bed level changes in the full-scale meandering river. It was found from the analysis of shear stress profiles that continual reductions in the magnitude of stresses had occurred along the intersection region of the bend channel. Percentage of maximum reduction in shear stresses was found to be of the order of ≈32% for cases of bend flow combined with low flood channel overflows and of ≈% 82 for combined bend and high flood overflows cases. In the latter cases, the reductions in stresses are strongly influenced by the local formation of stagnation and separation zones associated with a strong lateral outward currents developed at the intersection region of the main channel. On the basis of analyzing the shear stress behaviour, it was concluded that bottom levels changes in meander loop/neck cut-off situation are developed by high flood overflows conditions.

DOI:

Year: 1993