The study on control of sand bars and bank erosion in meandering rivers

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In the meandering river, the high velocity filament is shifted toward near the side bank and it leads to bank erosion. Disaster caused by the river bank erosion creates serious problems such as the people nearby homeless and the failure of river structures. Many disasters caused by the above situation have been reported. Therefore, it is important to make clear the mechanism of channel processes with bank erosion from disaster prevention point of view.At first, image processing of Landsat TM data was applied to survey river channel changes. The year to year changes of river channels, erosion areas, deposition areas and bars were clearly visualized by the processing technique. Based on the results, the characteristics of the channel process and an influence of flood magnitudes upon them were examined.Next we performed the experiments using the same sine-generated plan from having identical uniform sediment, whereas, the hydraulic condition was different in each of the cases. The morphol … More ogical processes were different in accordance with the imposed hydraulic condition.Finally, we developed a numerical model which can be used for both bed deformation and bank line shifting in 2-D plan form. The model was applied to the morphological behavior of experimental channels and actual rivers. In the case of experimental channels, the fundamental equations in a moving boundary fitted coordinate system are used, and the formulation of non-equilibrium sediment transport also is introduced to reproduce the phenomena accurately. Temporal changes in the plan form in a meandering channel are classified into two patterns of meander developing and straightening. Comparison of the observed and calculated results verified that the model is applicable to both channel processes under various hydraulic conditions. The initial development of meandering from a straight plan form also was analyzed using the model to clarify the effect of alternate bars on bank erosion. Lastly, the model was modified for the calculation of actual river processes with bank erosion. On the basis of the numerical findings, we discuss the effects of such hydraulic variables as the velocity distributions along the bank on the location of bank erosion and bed scouring. Less