Field and flume measurements of velocity, turbulence and dispersion are analyzed to investigate the stream diversity at two spatial scales, the cross-sectional and the reach scale. Due to the non-uniformity of the river beds and the variability with discharge rates, the investigated flows neither agree with the theory of two-dimensional boundary layers nor was it possible to identify systematic spatial structures. The dispersion results from the hydraulic impact of all morphologic features between two cross-sections. As a first approximation the slopes of the longitudinal dispersion coefficient and the ratio of the mean velocity and the square root of the energy slope are used to describe the observed variability among river reaches. This slope, denoted as dispersivity factor, is a useful parameter to assess the stream in non-uniform river reaches.