ESTIMATION OF THE QUANTITY OF SOIL LOSSIN THE THALWEGS OF THE STREAMS FORMED BY HEAVY RAINFALLS IN THE BREAKUP FURROWS AT ARABLE SLOPES:APPLICATION OF SATELLITE IMAGERY, GIS AND RADIOCESIUM METHOD
The paper presents some results of the study of natural-anthropogenic erosion network formation on open slope in the upper Oka basin (Orel region). On the example of 2014, it is shown that intensive precipitation (daily amount is comparable to the multi-year-averaged monthly amount), fell during the period when the field is not protected by vegetation (end of June and end of September, 2014), formed a breakup-furrow-based stream network. The satellite image collected on July 7, 2014 helped to detect this fact. Measurements of activity of the Chernobyl origin cesium-137 in the soil of thalwegs of the ancient ravines and modern streams (formed by the heavy rains of the summer and autumn of 2014 in breakup furrows), made it possible to estimate dependencies between cesium-137 activity and morphometric parameters of relief (catchment area and profile curvature) estimated by means of GIS for ancient ravines and modern streams. As a result of comparative analysis, it was found that the soil runoff on the Northern aspect slope in modern streams exceeds the runoff in the ancient ravines for more than 20 % (up to 50 %), while the values of catchment area are comparable. Soil runoff in modern streams can be predicted using the dependencies obtained for ancient ravines (applying corresponding raising factors) if June-September satellite imagery and precipitation monitoring data are available. Soil runoff in the tracks of agricultural machinery (with the 20 % evaluation error) can be estimated using equations obtained for interravine surfaces. Where streams cross ancient ravines, calculation of soil washout must be performed by dependencies obtained for ancient ravines.