Turbidity Maximum and Secondary Flow in a Cross-section of a Meandering Estuary: Chikugo River, Japan

摘要

The influence of a meander on a cross-sectional distribution of turbidity maximum was investigated by vessel-mounted ADCP in the estuarine channel of the Chikugo river. The along-river current was relatively week at the inside of the curve and was strong at the outside of the curve during flood tide. The cross-channel currents near the bottom flowed from the outside to the inside of the curve, and the suspended sediment concentration was high at the inside of the curve. These facts suggest that the secondary current occur in the meander of tidal channel and the suspended sediment transported by the turbidity maximum is moved into the inside of the bend. A fluid mud layer with a maximum velocity of 0.4 m/s was formed at the inside of the curve. The maximum thickness of the mud layer increased to 1.2 m during a flood tide, and it remained 0.1 m after one tidal cycle.