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Abstract

The sediment yield in the rivers of the Caucasus varies widely, reaching its maximum (> 2500 t km^-2 yr^-1) in the Eastern Caucasus. The sediment runoff of the Caucasus rivers is formed mainly during the warm season. Observations at gages generally showed a strong correlation between water and sediment discharge. However, direct measurements of streamflow and turbidity during extreme floods are rarely available because the measuring equipment is usually destroyed. Only gages in the foothills could reliably determine the suspended sediment load during floods. In this regard, reservoir siltation rates are a more robust data source about the contribution of extreme floods to the river sediment flux. Similar data can be obtained for small streams of the low- and high-mountain zones based on comparing the volumes of material delivered from the catchment slopes and their redeposition in the bottoms of the valleys located upstream of the gage. This study presents data on the contribution of extreme floods to the riverine sediment flux at various altitudes (from foothills to high mountains) and landscape (from subtropical to periglacial) zones of the Caucasus. The sediment yield associated with extreme events exceeded the mean annual sediment yield 4 -10 times, depending on the size of the river basin and landscape zone.This study was undertaken with the financial support of the Russian Science Foundation, project No. 19–17-00181 “Quantitative assessment of the slope sediment flux and its changes in the Holocene of the Caucasus rivers.”