Aim of the study:
The aim of the study was to characterise the hydromorphological units of a mountain river in terms of flow depth, flow velocity, bed shear stress, the Froude number and bed-material grain size.

Material and methods:
The study covered a mountain reach of the Skawa River, in which 8 pools, 8 runs, 5 riffles and 7 rapids were identified. In each of these units the dominant bed-material fraction was determined, and the water-surface slope, the instantaneous flow velocity (60 s at z/h = 0.4 from the bed) and the flow depth were measured at eight verticals representative of the unit. On the basis of the field measurements, the following characteristics of the distinguished unit types were determined and compared: bed-material grain size, flow depth, flow velocity, bed shear stress and the Froude number.

Results and conclusions:
Mean depths of individual pools ranged from 0.49 to 0.75 m, compared with 0.31–0.42 m in riffles. Mean point velocities were 0.348 m s⁻¹ in pools and 1.15 m s⁻¹ in rapids. The dominant bed-material fraction did not unambiguously distinguish HMU types. In the investigated Skawa reach and under the surveyed hydrological conditions, mean velocity, the Froude number and estimated bed shear stress differentiated pools, runs and riffles, but the applied comparisons did not detect significant differences between riffles and rapids in these variables. This finding does not exclude differences in other descriptors or under other flow conditions.