Causes and mechanisms of the disappearance of braided channel patterns (the example of the bia?ka river, western carpathians)

The channels of multi-threaded (braided) rivers occur commonly in areas that fulfill certain conditions such as substantial influx of bed material and gradients large enough to create significant energy of flowing wa-ter. Natural conditions favoring the formation of multithreaded channels are present in the Carpathians in Poland in Podhale - a large basin located in the piedmont area of the high-mountain Tatra massif. The area had experienced glaciation in the Pleistocene. Yet the 20th century - and especially its second half - was a period of rapid and irreversible elimination of braided channels across the region. The Bialka is considered to be the last braided river in the Carpathians in Poland. Many parameters like: structure (morphologic reach sequence), degree of braiding (BI index, W/D) and also a number of hydrodynamic ones (unit stream power, critical stress, shear stress, others) were investigated in order to assess a current stage of development of the Bialka river channel. The Bialka river channel appears to be a complex system with a differentiated structure. Its channel system is a mosaic of different types described by the following sequence: straight-sinuous-braided. It represents an intermediate type that is somewhere between a single-and a multi-threaded channel. Future evolution of the Bialka river channel appears to include further degradation and transformation into a poorer channel ecosystem.