Overbank sedimentation rates on the flood plains of small rivers in Central European Russia

摘要

The spatial variation and temporal dynamics of overbank sedimentation rates were studied on the flood plains of five rivers located in different parts of the Central Russian Plain. The radioactive isotope ~(137)Cs was used as a tracer for quantification of sedimentation rates. At least two morphologically typical flood plain segments were investigated along each of the rivers studied, with one sediment section sampled depth-incrementally at each of the studied segments to determine the Cs depth distribution. Both bomb-derived (1963-1964) and Chernobyl-derived (1986) ~(l37)Cs peaks could be reliably identified in most of the sections investigated. Thus, the vertical distribution of ~(l37)Cs in flood plain deposits permits the sedimentation rates for two relatively equal time intervals: 1964-1986 and 1986-present to be estimated. A clear trend of decreasing deposition rates is apparent for the last two decades. This can be attributed to recent land-use changes and climatic fluctuations.