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Turbulence measurements were carried out in compound channels with roughened floodplain. Mean flows are described through turbulence and secondary currents are explored through vorticity analysis. Turbulent intensities, turbulent kinetic energy and Reynolds shear stress are presented. Energy spectra are related to reveal the contribution of large horizontal eddies to the momentum exchange. Secondary currents influence velocity patterns in compound channels with and without vegetation. The secondary currents are stronger in the vegetated compound channel than in non-vegetated one under similar water depths. From results of vorticity analysis, an anisotropic turbulence is the main contribution to generation of secondary currents in both cases, but the Reynolds stress term is more important in the vegetated compound channel since vegetation generates wake turbulence rather than free shear turbulence. This is supported by the result of spectrum analysis.

Measurements of the turbulent fluctuations of the vertical and horizontal components of velocity, salinity and suspended solids concentration have been made near to the limit of salinity intrusion in a moderately high tidal range estuary. Velocity and salinity were monitored at four points up to 3 m above the bed and suspended solids concentration was monitored at 0·5 m above the bed. The data show that the vertical gradients created by solutes and particulate matter affect the velocity turbulence field and hence modify the turbulent mean velocity field. Turbulent fluctuations can be generated either internally or at the bed. The velocity turbulence field is shown to be dependent on relative depth, local gradient Richardson number and acceleration effects. The scalar turbulence fields are shown to depend on at least relative depth, the vertical component of the turbulent velocity fluctuations and the relevant scalar gradient. The mixing length functions used to quantify the turbulent transport processes are shown to depend on the local gradient Richardson number.

Turbulence measurements in a serpentine chlorine contact tank have been carried out using a two component laser Doppler anemometer for velocity. Mean velocities, turbulent intensities and Reynolds stresses have been presented. Concentration variations with time and space have also been obtained using two fluorometers. A detailed investigation of the flow structure in the tank inlet region shows the existence of free shear turbulent mixing, wall jet mixing and dead zones. Also the flow is nearly uniform and the concentration is almost the Gaussian distribution over the second half of the tank. The dispersion coefficient was obtained.

Measurements of salinity perturbations in a partially mixed estuary have been used to evaluate the usefulness of an inductive salinometer and to determine some of the characteristics of the salinity perturbations. The salinometer performed satisfactorily under most conditions. Although internal wave like effects were present, the turbulence fluctuations were dominant. The salinity fluctuations and the turbulent fluxes sw and su were found to behave in a manner similar to the density fluctuations in a thermally stratified atmospheric boundary layer and a laboratory open channel flow. A quadrant analysis suggested that the contribution of each quadrant to the turbulent flux changed with Ri. The turbulence parameters ν and cγ were found to decrease and increase respectively as Ri increases.

Measurements of turbulent fluctuations of the horizontal and vertical components of velocity and of salinity in the region 1-1·25 m above the bed have been made in the Teign estuary during parts of three ebb tides of different tidal ranges. The turbulent mean flow field determined from vertical profiles of velocity and salinity varied from well mixed to partially mixed depending on the relative importance of the vertical gradient promoting effect of shear and longitudinal density gradient and of the mixing effect of bed-generated turbulence. The turbulence parameters showed regular temporal trends. The relative intensity values for the new and existing data for the velocity components are strongly dependent on relative depth but not generally affected by Richardson number. The intensity of the salinity fluctuations increased with the salinity gradients. The vertical transport of momentum and the vertical Reynolds flux correlation coefficients decreased with Richardson number. The horizontal Reynolds flux correlation coefficient increased with Richardson number. These effects are tentatively explained by the concept of turbulent fluctuations being replaced by wavelike fluctuations in stable conditions. Results for momentum and solute mixing lengths help to substantiate previously published values.

Field measurements of vertical profiles of velocity and salinity along with turbulence measurements have been used to examine the effect of density gradients on the flow structure in the Great Ouse estuary. During the flood tide shear and longitudinal density gradients cause well mixed conditions in the lower part of the water column. In the upper part of the water column secondary flow effects induced by transverse density gradients, and acceleration effects can contribute to the formation of stable vertical density gradients. On the ebb tide the vertical density gradient appears to be the dominant factor which determines the structure of the flow. The velocity and shear stress data show the evidence of large scale motions which are consistent with the postulated flood and ebb flow structures.

Field measurements of the vertical and horizontal components of fluid velocity 0·43 m above the bed have been made with an electromagnetic flowmeter in a partially mixed reach of the Conwy estuary for parts of a flood and an ebb tide. The turbulent mean velocity and density fields showed different effects for flood and ebb tides caused by the interaction of shear and the longitudinal density gradient. The turbulent velocity parameters were generally dominated by bed-generated turbulence effects, but significant longer period contributions attributed to the shear-density interactions were detected. The shear-stress measurements made by two independent methods showed good agreement. The results generally show good agreement with previous less complete data. The use of the Richardson number to quantify vertical stability needs further consideration for partially mixed estuarine flows.