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Time series of in situ measured velocity and suspended sediment concentration from Qiantang Estuary (China), and estimates of turbulence and sediment stratification parameters are presented. The data span a period of 9 days, and after phase averaged, they are used to explore spring‐neap tidal variations in flow, turbulence, and sediment stratification. A local balance between shear production, sediment‐induced buoyancy flux, and dissipation is found to hold during ebb for both neap and spring tides. During flood elevated turbulence dissipation rates are observed, attributed to nonlocal turbulence, most likely due to horizontal advection. Our results show that the effect of sediment stratification is successfully parameterized by adding the Monin‐Obukhov length scale to the classical logarithmic layer theory. Flood‐ebb asymmetry in both Rig and Rf is observed, with higher values attained during flood due to the higher sediment concentrations and the corresponding weaker velocity shear found at these times. Rf is found to increase with Rig when Rig < 0.25, and it attains a maximum value of ~0.2. Our estimates, consistently with those from previous studies, fall slightly below the commonly used theoretical predictions. Sediment stratification contributes to the decay of turbulence, and weak mixing still exists under high Rig numbers.

Turbulent and flow structure associated with breaking tidal bores are deliberately investigated on the basis of field measurements. High‐resolution velocity and hydrographic data are collected in the middle Qiantang Estuary by a vertical array of acoustic Doppler velocimeters and optical backscatter sensors, collaborated with a bottom‐mounted acoustic Doppler current profiler. Besides obvious variations in diurnal and spring‐neap tidal cycles, the estuarine dynamics is featured by extreme asymmetry in flood and ebb tides. The flood tide is abnormally accelerated to generate tidal bores at the first 10 min or more, with breaking or undular configurations at the front. The occurrence of peak flow velocity, turbulent kinetic energy (TKE), and TKE dissipation rate (ε) is definitely associated with breaking bores, with their values several times to 2 orders of magnitude larger than the corresponding secondary peak values during the maximum ebb flows. Flow and turbulence dynamics are significantly affected by the tidal‐bore Froude number. A sandwich ε structure is clear exhibited with the maximum value at the surface, secondary maximum near the bed, and the minimum at the intermediate. Dual TKE sources are indicated by an approximate local balance between shear production and dissipation near the bottom, and a top‐down TKE dissipation using the modified Froude scaling in the vertical water column. The highly elevated dissipation by breaking bores is comparable to that by intense breaking waves in the surf zone, and the former potentially penetrates the entire water column to produce extreme sediment‐resuspension events in combination with intense bottom shear stress.

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