THE INFLUENCE OF SUSPENDED LOAD ON RIVER BED VARIATION IN THE BRAIDED RIVER OF THE ABE RIVER

Abstract

 We have studied the role of non-equilibrium sediment transport of bed load on bed variations of the braided channels in the middle and lower reaches due to flood flows in the Abe River, which is composed of a wide grain-size distribution of bed materials including gravels. This paper focuses on the role of non-equilibrium sediment transport of suspended load which is greatly affected by the three-dimensional flood flows on bed variation. Our calculations showed that the amount of suspended load is relatively large in the flood descending period, and the tendency for bed load and suspended load to accumulate on the sandbars resulted in a large specific height difference between the sandbars and channels. We also confirmed that secondary flows develop at the side edges of sandbars due to the flow mixing between the flow over the sandbars and the flow in the channels promote the deposition of suspended load at the side edges of sandbars, and it causes the lateral movement of the sandbar and reduction of the width of the channel.