EXPERIMENTS ON THE BANK EROSION DUE TO THE MEANDER ORIGINATED BY ALTERNATE BARS DURING DECREASING DISCHARGE

Abstract

 We often see bank erosion progress with meander flows in rivers on a large scale during decreasing discharge. However, it remains unclear how the decreasing discharge affects the meanders and the bank erosion. In this study, we performed hydraulic experiments, under varying discharge conditions, on the bank erosion due to the meander originating by alternate bars. The bank erosion rate increased about twice when the discharge was reduced compared with the case conducted under a steady condition maintaining the maximum discharge. The measurements of the plane flow velocity distribution in the experiments showed that the positional relationship between the flow driven to near the outer bank by the alternate bars and the bank line shape affects the bank erosion near the apex and the meander evolution. We have also observed that the change in the migration rate of bars in response to the decreasing discharge triggered the meander evolution.