Landform transformation and long-term sediment budget for a Chernozem-dominated lowland agricultural catchment

The loess hilly lands of the South-West Foreland of the West Carpathians are characterized by favorable climatic conditions, smooth topography, fertile soils and a long settlement history. For the first time, we document changes to human-induced landforms in a small zero-order dry valley (0.28km2) with Calcic Chernozem soils and develop a long-term sediment budget. The original surface was reconstructed based on interpreting records of erosion and deposition from 185 soil cores and six valley cross-sections. The topography inherited from the Pleistocene was transformed through lowering of hillslope ridges and convexities, along with infilling of shallow depressions within the original valley bottom. On convex-convex landforms had an average net erosion of −0.32±0.01m, while average net accumulation in the valley bottom was estimated at 0.20±0.01m. The correlation between change in soil profile depth with profile curvature (−0.51, p<0.01) was stronger than with slope (−0.42, p<0.01). The sediment budget was calculated using the Average Per Unit (APU) approach. When slope classes were used in calculating net soil loss from catchments was 143·103Mg·km−2, whereas 154·103Mg·km−2 was estimated when morphometric forms of hillslopes were used instead. Both values are <60% of estimates for similar loess catchments in Central and Western Europe. Prior to 1949, the landscape structure was characterized by small and narrow fields and vegetative field barriers that limited water and aeolian sediment fluxes in the direction of the thalweg and main wind directions. The landscape structure favoured the low-intensity tillage, erosion and accumulation within fields, and short-distance sheet and rill erosion on hillslopes. The land-use changes in the 1950′s caused removal of barriers for water and aeolian sediment transport, and changed the direction of sediment fluxes of tillage erosion. Past landscape structures should thus be considered when establishing and interpreting sediment budgets for lowland agricultural catchments.