This paper presents results of a field study to determine the flow characteristics and channel bathymetric patterns in a 4 km-long reach of the Middle Odra river with a special emphasis on the flood conditions. Characteristic features of this section are groynes and consecutively curved and straight river course. A series of measurements of flows, bottom tracking and water level has been carried out at varied discharges up to 756 m³ · s^–1 (mean flow equals to 180 m³ · s^–1) with water depths up to 6 m. River bottom consisted of sand and gravel, bed forms – dunes – reached a height of 1 m. The flow analysis divides river cross-section into channel zone between the groynes, zone of groynes and flood plains. The variation of Manning’s roughness coefficient with discharge and depth is determined taking into account the influence of the channel curvature. On the straight section the Manning’s coefficient moderately varies, once on the curved section significantly rises with discharge. The morphologic regime assessment, according to the Froude number locally up to 0,34, indicates possible transition, i.e. washing-out of dunes, however without a pronounced effect on the reduction of the flow resistance. From practical point of view, the effect/importance of sediment transport diminishes with flow, as the flow in main, regulated channel relatively diminishes when related to the total flow. Further, the determined roughness coefficients are at the upper, ‘save’ limit for the river channel conveyance analysis.

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