The Distribution of Water and Suspended Sediment Flow during Spring Flood in the Forked Channel of the Lower Ob (Within Khanty-Mansi Autonomous Area)

Abstract

The forked channel is a rare and poorly known type of branching channel, the distribution of flow in which is of key importance for water transport, economic activities, and water resources development. The article is the first to analyze the distribution of the flow of water and suspended sediments between the major two branches of the forked channel of the Lower Ob, i.e., the Malaya Ob and the Gornaya Ob, numerous floodplain channels (branches), responsible for hydraulic interaction between them and the Severnaya Sos’va, a large tributary of the Lower Ob. It is shown that water discharges vary widely in both branches because of the secondary separation of branch channels, the distribution of flow among branches, deviation of sometimes considerable part of flow into floodplain channels (branches) and its return further downstream. General tendencies are revealed in water flow distribution in forked channes, and the mechanisms governing water flow distribution between the branches are described. A considerable effect on the Malaya Ob is due to its hydraulic interaction with the Severnaya Sos’va through floodplain channels, which withdraw an appreciable portion of water flow of the former. The development of the channel of the Gornaya Ob features a considerable limiting effect of the right main bank. During floods, both branches of the forked channel of the Lower Ob, at low turbidity, show a tendency toward decrease downstream. However, the downstream decrease in the solid discharge is more pronounced, reflecting the general trend in sediment accumulation in the Lower Ob.