The Role of Lynchets in the Redistribution of Products of Anthropogenic Soil Erosion

This paper considers the features of accumulation of eroded soil material at the foot of the plowed slope and further to the side of the valley in the presence of a lynchet resulting from mechanical tillage on the lower border of arable land. A small catchment area in the area of intense Chernobyl pollution has been studied, where the position of the lower boundary of the arable land coincides with the upper boundary of the side of the valley over the past few decades. This made it possible to trace the spatial patterns of distribution of eroded material under conditions of stable functioning of the lynchet as an important lithodynamic boundary that accumulates and redistributes the slope runoff of sediments. The volume of material from arable slopes was determined using mathematical modeling of erosion based on a high-precision digital terrain model, climate data, soil erodibility, and crop rotations. The intensity of accumulation was estimated using 137Cs of Chernobyl origin as a reliable tracer. The bulk of the eroded material enters the valley network through a system of slope hollows that concentrate the slope runoff and cut through the valleys. In areas of the valley sides outside the runoff concentration zones, the redeposition of the material generally depends on the morphology of the arable slope, occurs locally, and is associated with episodic overflows as a result of the gradual filling of the depression before the lynchet. Under the existing conditions, the proportion of sediments accumulated on the sides of the valley is relatively low in the total sediment balance of the studied catchment area. Significant changes may occur due to a gradual reduction of the barrier role of the lynchet as a result of accumulation of sediments and climate changes that contribute to an increase in erosion rates.