Present-day denudation of a small alpine catchment of the Donguz-Orun Lake

Sediment dynamics in alpine catchments is highly variable both in time and space which should be considered in nature management. The study deals with investigation of the alpine catchment of the Donguz-Orun Lake, located on the northern slope of the Central Caucasus. We followed a morphodynamic approach to assess the denudation rate, which was supported by sediment delivery ratio assessment and two independent methods to verify the results. It was found that about 29,300 m³ of material is mobilized annually by the background exogenous geomorphologic processes in the catchment, corresponding to a local denudation rate of 2,2 mm/year. However, with an average sediment delivery ratio of 58%, only about 17,000 m3 reaches the catchment outlet, corresponding to the basin-wide denudation rate of 1,3 mm/year. Most of the sediment load in the lake basin is supplied by fluvial processes, predominantly gully erosion and sheet wash, as well as rock falls, glacial, and fluvio-glacial processes. Verification by independent methods, including estimation of sediment volume in the lake basin and the sediment fingerprinting technique, showed that used approach did overestimate the basin denudation volume by about 3000 m3. The total denudation of the catchment under study exceeds the average value for the high mountain zone of the Alps.