The paper discusses the hydro-morphological changes in the mountain stream Targaniczanka caused by the violent flood flow on the 24th August 2005. The flood destroyed or damaged road bridges located in the middle and lower reaches of the stream and affected buildings situated too close to its channel. The course and effects of this event were analysed on the basis of stream basin parameters, rainfall, flood wave travel, stream cross-sections, rating curves, and the grain-size distribution of bed material. Since the Targaniczanka Stream catchment is uncontrolled, the discharge during the flood was described using a rainfall-runoff model. The grain size measurements made it possible to determine the bed stability conditions which, combined with the measurements of cross-sections, provided the basis for establishing bed roughness and the discharge capacity curve. The hydraulic parameters of the stream bed after the flood were compared with the results of simulation run for a stable cross-section. The frequent occurrence of rapid outflows in the stream may be attributed to the morphology of its basin. The flow that occurred on the day in question substantially exceeded Q1%. The fact that the hydrodynamic stability of the stream was upset and many bridges were damaged suggests that the infrastructure of the stream should be redesigned.

37-48