Contemporary erosion and suspended sediment yield within river basins in the steppe of the Southeastern part of the Russian Plain: A case study of the Samara River basin

Abstract

The paper presents the results of contemporary trend assessment in general erosion intensity within the southeastern steppe sector of the Russian Plain, a case study of the Samara River (the upper reaches) basin (22,800 km2, Orenburg oblast, European part of Russia), based on the long-term studying of river suspended sediment yield dynamics. The assessment is supplemented by accumulation rates field study of the soil-rill-gully erosion products in a typical small catchment (the catchment area is 1.92 km2) of the river basin using environmental radioactive caesium-137 (incl. Chernobyl-derived 137Cs) as a chronomarker. The results obtained clearly show that the Samara River’s suspended sediment yield has been reduced at least twice over the last 30 years compared with 1940–1960s. The marked decreasing trend in the erosion intensity in the Samara River basin is confirmed by a decrease (by 3.0–3.6 times as a minimum) in accumulation rates of the erosion products over the past 60 years within the dry valley bottom of the studied small catchment. The main reason for such significant erosion rates reduction was a decrease in surface snowmelt runoff within the basin area since the early 1980s, associated with a reduction in a soil freezing depth and a general increase in air temperature during spring months.