INHERITED FLOODPLAINS AND REGIME OF SEDIMENTATION IN RIVERBED – FLOODPLAIN COMPLEXES

Abstract

During circumpolar distribution of the large rivers with large streamflow the wide floodplains with high amplitude relief were formed in their valleys. While the discharge of the river diminished this relief was partly reformed in the course of the lateral reformations of the river channel and ancient floodplains on the large areas took on inherited character. Due to their wideness inherited floodplains serve as a effective barriers between the erosion part of the river system (erosion furrows on the slopes and gullies) and balka-river part where transit and accumulation of the sediments by the most part take place. The most part of the sediments from gullies and slopes accumulates on the inherited floodplain. In the result there is very low correlation of sediment transport regimes even between close ranges of the river. Dating of the sediments proves that as largest basins on the floodplain are being infilled and the level of the floodplain rises, the rate of accumulation and barrier effect diminish. At last the inherited floodplain relief changes totally due to lateral and vertical river bed deformations and sediment transport in this river range is being retrieved.