Riverbank erosion and evolution of channel forms as factors of river channel network transformation

In the article we discuss basic schemes of river channel reshaping. It changes their morphodynamic type, as well as the structure of river channel network, especially on branched rivers. Riverbank erosion within channel and branch meanders leads to the formation of a passage between river channels, including branches of bifurcated channels, and between the main channel and floodplain channels or channels of the lower reaches of tributaries (small rivers) in the rear parts of a main river floodplain. The result is the splitting of bifurcated channels, transformation of a channel into a branch or, conversely, a branch into the main channel by water interception, as well as formation of floodplain-channel branches, sometimes with three or four channels, through redistribution of water flow. Herewith unusual types of branching occur in some cases. The development of cut-off bends in meandering channels could become a key factor for the formation of a bifurcated channel and the distribution of water flow along newly formed branches. Complex changes in the structure of river channel network are characteristic of the junction points of meandering rivers. All these transformations result from the (self)-evolution of channel forms and the riverbank erosion, and do not involve changing factors of channel processes, e. g. water flow and sediment transport. This should be taken into account in paleochannel and paleohydrological reconstructions, predicting river channel deformations and designing regulation measures for water economy and water transportation projects.

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