Sediment Yield in the Caucasus Mountains and Its Trends as a Reflection of Climate Change and Anthropogenic Impact

Abstract

The sediment runoff of mountain rivers is an important characteristic that reflects the intensity of denudation in various altitudinal zones, as well as the spatial and temporal features of its changes. The Caucasus region, which includes the Greater and Lesser Caucasus, is characterized by significant territorial contrast associated with differences in the geological and geomorphological structure, seismo-tectonic activity, climate, which together determine the lifestyle of the local population and the features of anthropogenic impact on landscapes. The paper presents the results of estimates of the contemporary rates of denudation of the region, obtained on the basis of processing a database on the flow of suspended sediments of rivers at 194 gauge stations with a duration of observations of more than 10 years. To identify the influence of the main natural and anthropogenic factors on the sediment runoff of rivers, calculated and published data on spatially distributed indicators characterizing individual factors or their combinations were used. Statistical processing of dependencies between individual indicators and sediment runoff of rivers was carried out. It has been established that the mean suspended sediment yield (SSY) for the region is 446 t km–2 yr–1. It reaches its maximum values (SSY 1500 t km–2 year–1) in the Eastern Caucasus, where it has remained high in recent decades and continues to grow in a number of river basins. For other parts of the Greater Caucasus, a trend of decreasing sediment runoff was revealed, due to a decrease in the glacial supply of rivers and, more locally, a decrease in the area of arable land in the mountains.