High-gradient stream, Channel-reach morphology, Bankfull geometry, Flysch, Western Carpathians

A channel-reach morphology of mountain headwater streams results from the balance between ?uvial and hill- slope processes. A large dataset (n = 102) of channel-reaches coming out from ?ysch mid-mountains was evaluated and compared with streams occurring in other environments. Two new channel-reach morphologies were distinguished with respect to their differences in the ratio of sediment supply to transport capacity: bedrock-cascades and step-rapids. The chaining of channel-reach morphologies by gradient criteria and the parameters of channel gradient and bankfull width related to the basin area show similar trends, when compared to other recent studies. By contrast, bankfull depth indicates its independence on increasing basin area. Signi?cant downstream coarsening of bed material occurs only in alluvial stepped-bed morphologies (cascades, step-pools and step-rapids) mainly due to strong slope-channel coupling processes.