Home – Home – Jornals – Geography and natural resources 2018 number 1

For the first time, a detailed analysis is made of the occurrence and different morphodynamical type-channel formation conditions on the Middle Ob within Tomsk oblast, from the mouth of the Tom river to the boundary with Khanty-Mansi Au tonomous Okrug-Yugra. We emphasize the role of a broad floodplain and of its inundation conditions during snowmelt floods, the occurrence conditions for channel-forming water discharges and channel stability in the predominant development of river meandering, including of the branches of floodplain-channel forks. Braided and straight unbraided channels occupy a subordi nate position separating sinuous reaches. It is shown that floodplain-channel forks with meandering branches occur largely at long transitions of the river from one valley side to the other, diagonally across the floodplain flow direction. The parameters of the bends in the forks of this type correspond to their hydraulicity, but no clear-cut hydrological-morphological relationships are determined because of intermittent runoff redistributions between branches. Modal (for the sections of the river between the main tributaries) values of the parameters of the bends depend inversely on the river hydraulicity (order). By introducing a correction coefficient for floodplain dissection by a floodplain fork as the indicator of the degree of diversion of water flow from the channel to the floodplain, it was possible to determine a “normal” relationship between parameters of the bends and hydraulicity of the channel flow during floods. Furthermore, we ascertained the relationships between the degree of development and the coefficient of the form of bends and determined their manifestations. For all the bends, we determined changes in parameters for the time interval 1986-2011 and the transition of some of them from one category to another, and ascertained the causes for runoff re distribution and the development of branches of the floodplain-channel forks.