The knowledge of the morphological dynamics of water courses is essential to approach the management problems, such as reservoir sedimentation and minimum instream flow, generated by river barrages. Comparing test observations for two reservoirs in Basilicata (Italy), this paper shows how the effectiveness of the hydraylic works, aimed to reduce sediment transport along the fluvial network and prevent part of the sediment discharge from reaching the lake, is dependent on the river type. With reference to the weir on the River Basento, the present review suggests that fluvial modelling phenomena knowledge playies a preminent role on the possibility to define a method to calculate the minimum ecological discharge in braided alluvial beds downstream from weirs
