Measurements of Turbulence and Suspended Sediment in Tidal River

Abstract

Simultaneous measurements of instantaneous velocities (longitudinal and vertical), suspended sediment, and salinities are performed continuously during two spring tides in the Ota River estuary. The velocity sensors are fixed at three heights above the bed and a turbidity sensor is located near the bed. Although the vertical sediment fluxes occur intermittently (as well as the vertical momentum fluxes), the longitudinal sediment fluxes are not very intermittent and the fluctuations of suspended‐sediment concentration are linked to the sign of u in spite of the w sign. The fractional contribution curves to the vertical sediment flux are similar to those for the Reynolds shear stress. The patterns of conditionally averaged fluctuating velocities indicate that the large positive fluctuations of suspended concentration occur immediately after the transition from the positive to negative of u and the suspended‐sediment concentration decreases at the early stage of the positive u. The sediment suspension is related to the large‐scale turbulence together with ejection motions; this large‐scale turbulence is probably associated with the cluster of ejections.