THE MEANDERING AND ANABRANCHING CHANNEL OF THE LOWER IRTYSH

Abstract

This paper is the first to describe the conditions and features of the channel formation for the lower Irtysh (from the city of Omsk to the confluence with the Tobol River), with a focus on the formation of the channel’s bends and branches at various structural levels. Basing on the geological and geomorphological structure of the river valley, we divided the Irtysh into ten sections, each of which has its own characteristics of the distribution of channel types, their parameters, and transformations. The portion of the Irtysh River from Omsk to the Tobol River mainly meanders, and its bends are often complicated by islands in the near-top parts, on their upper wings or on rectilinear ‘inserts’ of large adjacent bends the tops of which are located at opposite sides of the valley bottom or islands being an element of sinusoidal and finger-shaped bends. At the beginning of the section, channel (island) branchings are common, mostly single and one-sided, being 112 km in total length, which is 9.6 % of the length of the river (from Omsk to the mouth of the Tara River). The results obtained are of great importance for the water management and water transport development of the river.