Layering of natural territorial complexes in river floodplains as a function of channel and hydrological processes

Layering of the morphological structure of the floodplain landscape is determined by the weakening of the influence of fluvial factors and the increasing role of non-fluvial factors with distance from the river and with the floodplain height rise. Tier is the high-rise floor of the floodplain landscape structure, the morphology of which is due to the kind of horizontal and vertical channel deformations prevailing during its formation, and the uniformity of the natural territorial complexes and its components (primarily vegetation, as most mobile) is provided by the stability of the hydrological regime. Layering is the basis of the traditional division of the floodplain into low, medium and high levels, but usually on the floodplains of large rivers there can be traced from 5 to 7-10 tiers. It is expressed on the streams at facies grade, and tiered location of the natural complexes is visible on the slopes of the valley. At the medium river floodplains tiers are formed from stows, on large river floodplains - the complex stows and even localities. The increase in discharge of the river increases the amount of layering options in its floodplain. For stream floodplains can only be one or two options, on the floodplains of large rivers there are 15-20 and more options, for the forest, meadow complexes, for the complexes of the manes, troughs, other elements of the floodplain relief. On step floodplains incising rivers layering of the natural complexes is expressed better than on the flat and banked floodplains with dominated accumulation. At the 12-meter high-rise Yenisei floodplain interval tier reaches 2.5 m, at the 5-meter Ob floodplain below the confluence of the Biya and Katun rivers - 1.5 m. On the accumulation river floodplains tier high-rise intervals rarely exceed 0.5 m, which blurs the boundaries of tiers, and reduces their quantity. On a very wide flat floodplains layering is replaced by a horizontal differentiation of the natural territorial complexes, since the duration of flooding depends not only on the height above the water level, but also on the ability to access water for one or another array. The tier clarity is determined by the regular flooding. Layering step floodplains is always the same type (direct): from primary, weak turf-covered by pioneer sedges and grasses bed forms and young shrub floodplains lower tiers to mature high arrays with the forest and meadow vegetation and to the zonal complexes on terraces and non-flooded areas. Layering on the accumulating rivers floodplains is more complicated. Here are two common types - for riverbed complexes and for hydromorphic complexes in the interior part of the floodplain. The latter is characterized by the proliferation of peaty marsh complexes at low levels, meadow-shrub and forest complexes - in the higher. In exceptional cases, if the channel is above the banked alluvial plain, we can see the reverse layering - riverbank floodplain systems, located on levees, can be positioned hypsometrically above close to the zonal complexes on its main rarely flooded surface. This situation is typical for the floodplains of the Amu Darya in the foothills, the Yellow River within the North China Plain.

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