Present-day downcutting of the Raba River channel (western Carpathians, Poland) and its environmental effects

Timing and causes of the present-day channel downcutting of Carpathian tributaries to the Vistula River are exemplified by a case study of the Raba River, a gravel-bed stream characterized by great variability of water stage and discharge. Up to 3 m of river incision has occurred since the beginning of the present century associated with an increase in stream power caused by river-control works, and reduction in bed-material load linked to changes in basin management. Gravel extraction from the channel and modifications in flood flows have increased rates of incision over the last thirty years.Lowering of ground-water levels on the valley floor, increase in river-bank susceptibility to erosion, decrease or cessation of overbank-sediment accretion, and impoverishment of plant and animal communities of riverside biotopes are the principal environmental effects of channel downcutting.