Aim of the study:
The aim of the study was to determine the parameters of the stream transport capacity using turbulent diffusion coefficients using the imaging technique and to compare them with the coefficients obtained as a result of the measurement with the ADV (acoustic Doppler velocimeter) probe in a compound channel.

Material and methods:
Model tests were carried out on a physical concrete model of a straight open channel with symmetrically complex trapezoidal cross section. On the model, the study of particle motion was carried out using the digital image recording technique with the analysis of the motion of the dosed indicator (solid particles), (PIV) (Particle Image Velocimetry), allowing to determine the basic parameters characterizing the process of their transport in the subsurface layer of water in the channel.

Results and conclusions:
Primary analysis of test results obtained in laboratory conditions using the PIV (Particle Image Velocimetry) technique based on particle trajectory (in Lagrange’s approach), in comparison with the results of calculations of turbulence characteristics based on measurements with the ADV probe (in Euler’s approach), show significant differences between the results obtained. Turbulence intensity, vortex length, and values of turbulent diffusion coefficients, calculated on the basis of Lagrange’s autocorrelation function, are much higher than the values calculated according to Euler’s function.