Assessment of contemporary erosion/sedimentation rates trend within a small cultivated catchment using the radiocaesium-137 as a chronomarker (a case study from the Udmurt republic, European Russia)

Abstract

This paper is devoted to revealing and estimating the contemporary soil erosion rates trend within arable lands in the south of the forest zone of European Russia, based on the study of sedimentation rates at a small dry valley bottom with almost completely cultivated catchment slopes. The dry valley catchment (0.68 km2) is located in the south part of the Udmurt Republic (the mixed forests zone) within the Izh River basin. The bomb-derived and Chernobyl-derived radiocaesium–137 was used for dating valley bottom sediments in two time intervals: 1954(1963)–1986 and 1986–2016. To analyze the causes of change in sediment redistribution rates, morphological and morphometric analyzes of the valley, the results of year-to-year observations for gully heads retreat in the catchment vicinities, hydrometeorological observations of the Russian Hydrometeorological Survey network, and also aero- and satellite images across years were used. There was a noticeable decrease in the sedimentation rates of washed-out soil material from the catchment slopes at the valley bottom over the past 60 years: from 1.8–2.5 cm/year during 1954–1986 to 0.15–0.75 cm/year for 1986–2016. Hence, the sedimentation rates have decreased by 2.5–3 times as a minimum. This trend is consistent with a decline of the average retreat rates of gully headcuts within cultivated lands in the Udmurt Republic over the past 40 years — from 1.3 m/year in 1978–1997 to 0.3 m/year in 1998–2014. We suppose that the main reason for such significant reduction of erosion rates was a increase in protective crop coefficient associated with a increase in the proportion of perennial grasses since the late 1980s. Additional contribution to the erosion reduction was owing to a decrease in surface snowmelt water runoff within the catchment area since the early 2000s, associated with the reduction in soil freezing depth and general increase in air temperature during the winter and spring months in this region of the Russian Plain.

Contemporary Trends in River Flow, Suspended Sediment Load, and Soil/Gully Erosion in the South of the Boreal Forest Zone of European Russia: The Vyatka River Basin

“…This trend coincided well with a decrease in gully head-cuts retreat rates within plowed catchments in the Udmurt Republic over the past 40 years: from 1.3 m y -1 in 1978-1997 to 0.3 m y -1 in 1998-2014, i.e., by 77% [23]. We [55] also found a commensurately significant decrease in the rate of accumulation of washed-out soil in one of the small and almost wholly cultivated dry-valley catchments of the Udmurt Republic, located in the Izh River basin (see Figure 1), which adjoins the Vyatka River basin from its southeast. So, in 1954-1986, the washed-out soil material accumulation rates in the dry-valley bottom of this catchment ranged from 1.8 to 2.5 cm y -1 , while in 1987-2016, they ranged from 0.15 to 0.75 cm y -1 , i.e., decreased by at least 2.5-3.0 times.…”

Contemporary Long-Term Trends in Water Discharge, Suspended Sediment Load, and Erosion Intensity in River Basins of the North Caucasus Region, SW Russia

“…Finally, mention should be made that the above-mentioned hydrological (a reduction in spring snowmelt-induced discharge) and sheet/rill/gully erosion intensity changes (a decrease in annual river load/yield) in the basins of the main studied plain rivers of the Ciscaucasia (the Kalaus River and the Kuma River), in river basins of the central part of the northern slope of the Greater Caucasus (the upper Terek River basin) and possibly the lowland part of the Kuban River basin, were similar in their common features to those previously described in many regions of the neighboring East European Plain [13][14][15][16][17][19][20][21]23,25,[27][28][29]71,73,83,84], in the Baltic countries (Estonia, Latvia, and Lithuania) [85], as well as in Eastern Scandinavia [86], Poland, Belarus, and in the north of Ukraine [87]. That is, it was a sizeable regional phenomenon for Eastern and Central Europe.…”

“…For instance, tendencies towards a decrease in the intensity of sheet/rill/gully erosion processes, the accumulation of their products, and also a reduction in river sediment load/concentration have been found over the last decades in many administrative regions and river basins of the forest-steppe and steppe zones of European Russia characterized by a relatively high degree of agricultural development. All of this was possible by using various approaches and methods, such as modeling [17,18], analysis of hydrological (suspended sediment load) data [19][20][21], stationary studies [22], field and remote monitoring [23][24][25], field research based on a variety of chronomarkers [26][27][28][29], and so on. Despite these and other numerous results, many of European Russia's regions are still "blank spots" regarding this field of research.…”

Integration of Data of the Remote Sensing, Gis, and Gamma-Spectrometric Analysis to Study Soil Material Redistribution

“…Existing recommendations on estimation of soil material redistribution in arable areas of upper parts of the drainage basins assume layer-by-layer on depth soil sampling (Belyaev et al, 2013;Gusarov et al, 2019;Owens, Walling, 1996;Sharifullin et al, 2018;Walling, He, 1997) followed by plotting the vertical distribution of caesium-137 radioactivity and allocation of the soil layers that mark the radioactivity of the soil material in 1986 (the year of the Chernobyl accident). In the case of spatial interpolation and estimation of slope morphometry influence onto the soil runoff, a comparative analysis have to be carried out for the slopes separated (zoned) by the exposure parameter.…”