Precise sediment flux assessment of a small ungauged low-mountain catchment in the North Caucasus

Abstract

Abstract Soil erosion and sediment export from hillslopes are significant problems associated with agriculture, especially in parts of the world where society is already living in extreme environments. In particular, mountainous environments remain severely understudied, with only a few runoff and sediment transport measurements available. It is necessary, therefore, to develop and validate independent methods that do not rely on long-term observations at gauging stations. Here we used three independent methods to predict soil erosion and associated sediment yield (SY) from a 1.84 km² basin in the North Caucasus. The first part concerns assessing the sedimentation rate, which was made using in-situ measurements of volumetric sediment deposition rates. Secondly, we look at the connectivity of sediment sources and the lake. A combination of remote sensing data and field surveys was used to estimate sediment connectivity and erosion mapping. The third part regards the computation of soil erosion using the Revised Universal Soil Loss Equation (RUSLE). There are three major findings in this study that help us understand sediment redistribution patterns in mountainous areas. First, based on the lake sedimentation rate, we found that the mean annual area-specific sediment yield is 514 (95% CI, 249–839) t km− 2 yr− 1. Similar results were obtained from the erosion mapping (i.e., a map of erosion processes) — 428 (95% CI, 322–546) t km− 2 yr− 1. Secondly, the spatial distribution and rates of the erosion processes suggest that sheet and rill erosion are responsible for ca. 40% of total sediment export, slides and rockfalls — 18%, while the rest is removed by soil creep. Additionally, the RUSLE-based modelling of sheet wash and rill erosion has highlighted the areas most prone to soil erosion. The corresponding mean annual soil erosion rate of 1.59 mm yr− 1 was very close to the results obtained from the literature review.