Influence of relief characteristics and landscape connectivity on sediment redistribution in small agricultural catchments in the forest-steppe landscape zone of the Russian Plain within European Russia

© 2018 Elsevier B.V. Sheet, rill and gully erosion occurring in the snowmelt period (March–April) and rainfall season (May–September) is the main factor of soil degradation and mobilized hillslope sediment redistribution within cultivated lands of the Russian Plain. The evaluation of sediment redistribution for the period since 1986 within catchment sediment cascades was done based on an integrated approach for some representative dry valley catchments located in the western (the Plava River basin, Tula Oblast, Russian Federation) and eastern (the Temeva Rechka Creek catchment, the Myosha River basin, Republic of Tatarstan, Russian Federation) sectors of the forest-steppe landscape zone of the Russian Plain. All the catchments studied are characterized by a high proportion (within the range of 60–80%) of cultivated lands. The modified version of the Universal Soil Loss Equation (USLE), the Russian State Hydrological Institute's erosion model, and the LandSoil erosion model were applied to calculate soil losses within the cultivated lands. The morphological classification of interfluve slopes and hollow slope catchments, in combination with the sediment delivery ratio (SDR) assessment for slopes and hollow slope catchments of different configuration, were used to assess sediment transfer from the cultivated lands. The Chernobyl-derived 137Cs isotope was applied as a chronomarker for sediment dating in different sediment sinks located along pathways from cultivated slopes to river valley bottoms. We found that the morphological features of the dry valley catchments, including a pattern of the dry valleys of different Hortonian orders, dry valley and hollow density, dry valley incision depth, and proportion of slopes and hollow slope catchments of different configurations are the main parameters that determined a proportional input of the different sediment sinks to the sediment interception along the pathways from the cultivated slopes to the river valley bottoms. The land use/cover features are mostly responsible for the pattern of buffer zones within the interfluve parts of the catchments. The quantitative assessment of the sediment budget allowed us to conclude that the mean SDR coefficients for the dry valley catchments of second, third, and fourth Hortonian orders are 0.56, 0.33, and 0.07 respectively. The extrapolation of the study results of sediment redistribution evaluation, obtained from the studied catchments located within the Plava River basin, to the entire basin of the river also allowed us to evaluate the mean value of hillslope-to-river-valley-bottom SDR = 0.27