Islands of the upper River Ob: morphometric characteristic, evolution and dynamics

The studied reach of the upper River Ob is quite complicated in the morphological aspect and characterized by very low channel stability and high discharge of sand load. Unconstrained conditions for lateral channel migration promotes active channel deformations not only at long-term scale, but also seasonally. Channel deformations contribute to the transformation of the channel and its morphodynamic type in time. The upper River Ob is intensively used as a water course, so any reorganization of the channel and river islands should be taken into account to support navigation. Morphometric and morphodynamic analysis of the islands made it possible to develop their morphological classification. Morphometric parameters of islands, being associated with the characteristics of the channel itself, are one of the main classification features. Empirical relations were obtained that link the dimensions (Lo, Bo) and shape of islands (Lo/Bo) with the morphodynamic channel type and its stability, the degree of branching of the channel (number of islands no per 1 km of channel length x). The features of island dynamics are also determined by the morphodynamic type of the channel and are associated with the morphometric characteristics of the islands themselves and their position in the channel, which determines the transgressive, regressive and transverse shift or their stable position in time.