ИСТИНА

Understanding and quantifying catchment sediment fluxes is vital from both a scientific and environmental management standpoint. This research explores the combined effects of catchment complexity in topography, tectonics, climate, land use patterns, and lithology on the Suspended Sediment Yield (SSY [t/km²/year]) in the Caucasus region. By analyzing results from 244 gauging station measurements, we identified the primary controls on the SSY. Due to the high multicollinearity of predictors, we applied a Partial Least Square Regression (PLSR) to clarify the connections between SSY and explanatory variables. Correlation and partial correlation analyses revealed that topography proxies such as Height Above Nearest Drainage (HAND) and Normalized Steepness Index (Ksn) are among the most significant. However, PLSR analysis suggested that the influence of these variables is likely associated with Peak Ground Acceleration (PGA). We also found a strong relationship between various land cover types (e.g., barren areas and cropland) within different elevation zones. To further understand the impact of land use and climate change on sediment load, we studied temporal change in suspended sediment discharge (SSL [kg/s]) in the Terek and Kuban River basins (North and West Caucasus) during the Anthropocene. We used mean annual SSL measured at 50+ unregulated gauging stations. Our analysis revealed a statistically significant average decrease of 1.17%/year in SSL. The CUSUM and double mass curve analyses suggested a transition year of 1988-1994 in most cases, likely due to a decrease in glacier and arable land areas resulting from climate change and the collapse of the USSR. This is particularly critical for catchments with a high cropland fraction in the foothill belt (<500 m a.s.l.). The results were less clear for high-altitude (>1000 m a.s.l.) catchments. However, there are several reasons to believe that high-altitude gauging stations are less exposed to a significant reduction in suspended sediment load.