ИСТИНА

Paper presents an application of the Chernobyl-derived 137Cs for quantification of floodplain aggradation rates for the Plava River by detailed sediment sampling at 4 representative floodplain segments. Two approaches have been employed for assessment of the post-Chernobyl (1986-2009) floodplain accumulation rates. The first approach is based on identification of the Chernobyl fallout-associated 137Cs peak in overbank sediment sections. The second approach involved quantification of the total isotope inventory increase at individual sampling points associated with the post-Chernobyl deposition of contaminated suspended sediment. Highest deposition rates (up to 14 mm/year) was found for the lower floodplain level Combining this information with areas occupied by different floodplain levels within the investigated 54 km long valley section determined by detailed geomorphic surveys of the selected reaches, it has been estimated that about 7500-9000 m3 of sediment have become stored on floodplain over the 1986-2009 period. It was underlain that application both Chernobyl-derived and bomb-derived 137Cs for sedimentation rates dating allowing to receive quantitative characteristics of floodplain deposition rates dynamic in different part of Europe.