ASSESSMENT OF OVERBANK SEDIMENTATION RATES AND ASSOCIATED POLLUTANT TRANSPORT WITHIN THE SEVERNYA DVINA RIVER BASIN

Abstract

It is now widely recognized that significant proportion of pollutants in rivers is transported with suspended sediments. This paper presents a combination of reconstruction of recent floodplain sedimentation rates based on detailed description of sediment sections and 137Cs stratigraphy with geochemical analysis of overbank deposits at selected sites on rivers of the Severnaya Dvina River basin. Overbank sedimentation rates for sections sampled on floodplains of the Severnaya Dvina and Vychegda Rivers are characterized by noticeable decrease from ≈1.5–4.0 cm/year between 1954 and 1963 to <1.0 cm/year at present. It can be explained by the natural evolution of the floodplain segments sampled. In contrast, highest modern floodplain aggradation rates (≈1.8 cm/year) observed for the relatively small Toshnya River are definitely associated with human impact—locally intensive agriculture. Evaluation of geochemical properties of overbank sediments has shown that general levels of the sediment contamination by heavy metals are low.

Keywords

• suspended sediment
• floodplain
• overbank deposition
• 137cs
• particle-bound pollutants
• severnaya dvina river