Aspects of Sediment Transport in Single-Thread and Anabranching River Channels in Flysch Carpathians (A Case Study from the Czech Republic)

Present-day state of channels shows a tendency towards the acceleration of processes linked with river bed lowering. Focusing on the Ostravice River and Bečva River basins in the Czech part of flysch Carpathians, the paper summarizes the results of energy potential aspects of contemporary Carpathian river channels. The study has been conducted with the use of the Bedload Assessment for Gravel-bed Streams (BAGS) spreadsheet-based program and unit stream power formula. Presented results show potential values of sediment transport with the identification of erosion and accumulation processes in channels. Selected channel cross-profiles include preserved gravel-bed reaches with an anabranching pattern as well as transformed reaches with accelerated deep erosion and occurrence of a single bedrock channel. The modelling shows potential transport trends in relation with the morphology of the channel. The results can be used to distinguish the reaches with erosion or accumulation trends. The modelling on cross-profiles with a low rate of fluvial erosion (anabranching channel pattern) shows a decrease in potential sediment transport. It is caused by increased or decreased (dis)connectivity in the longitudinal profile of the fluvial (dis)continuum system. It is influenced both by flow diversion through sub-channels and a decrease in sediment transport capacity. We define this area of active channel as a zone of reduced growth in transport capacity. In contrast, reaches with a single channel pattern show higher values of potential sediment transport caused by the absence of this zone of reduced growth in transport capacity. The results may be applied in form of a conceptual scheme to improve the management of local watersheds.