Nadezhda Nikolaevna Ivanova

The paper considers the spatial heterogeneity of the flow of eroded soil material to the foot of the plowed slope and further to the side of the valley in the presence of a lyncahrt resulting fr om mechanical tillage on the lower border of arable land. A small catchment area in the area of intense Chernobyl pollution has been studied, wh ere the po- sition of the lower boundary of the arable land over the past few decades coincides with the upper boundary of the side of the valley. This made it possible to trace the spatial patterns of the distribution of eroded material with stable functioning of the lynchart as an important lithodynamic boundary accumulating and redistributing the slope runoff of sediments. The determination of the volume of material coming from arable slopes was carried out using mathematical modeling of erosion based on a high-precision digital terrain model, climate data, soil erodibility and crop rotations. To assess the intensity of accumulation, 137Cs of Chernobyl origin was used 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 the areas of the valleys sides outside the runoff concentration zones, the re- deposition of the material mainly depends on the morphology of the lyncahrt, occurs locally and is associated with episodic overflows as a result of the gradual filling of the depression before the lyncart. Under existing conditions, accumulation on the sides of the valley occupies a relatively small share in the total sediment balance of the studied catchment area. Significant changes may occur due to a gradual decrease in the barrier role of the soil as a result of sediment accumulation and climatic changes that contribute to an increase in erosion rates.