Classification of river islands
G.B. GOLUBTSOV, R.S. CHALOV
Lomonosov Moscow State University, Moscow, Russia
Keywords: channel processes, typification of islands, channel stability, flow dispersion, morphodynamic type, Karasev criterion
Abstract
The analysis of various types of islands occurring on rivers with a branched channel or on meandering rivers was carried out, which made it possible to classify the islands taking into account the features of their formation, development and dynamics, as well as depending on the characteristics of the channel itself. Six main categories of islands have been identified, associated with their characteristics and conditioned by genesis, position in the channel, compliance with a particular structural level of branching, shape in plan (hydraulic resistance exerted by the island on the flow), and age. In addition to the main factors, the classification of islands is influenced by the characteristics of the channel itself, among which we can note its widening (the formation of an island in local widenings of the channel or due to the splitting of the flow into two or more branches of the current), stability, which determines the size and number of islands in each branching node, which, in turn, is directly related to the dispersion of the flow along the branches. Separately identified are the types of islands formed by sand or pebble-boulder deposits, differing in the degree of resistance to the impact of the flow (intensity of erosion of the headland) and in the development of the floodplain facies of alluvium and floodplain soils, which determines the type and nature of vegetation on the island. The considered classification features take into account the main function of the islands, such as flow dispersion, and can be applied when considering the water transport use of rivers.
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