Debris Flow Morpholithogenesis in the Central Part of the Sayan-Baikal Stanovoi Highlands

Аннотация

Presented are the results from studying transported and suspended load formed during the debris flows and floods within the basins of small rivers in the central part of the Sayan-Baikal Stanovoi Highlands. In studying deposits of suspended and transported load exposed by profiles on alluvial fans, the age of the debris flow event was determined by radiocarbon dating of organic matter of buried soils. The turbidity of the flow, its speed, water discharge, pH, total mineralization of water and mudflow suspensions, and particle size distribution of suspended material were estimated for suspended load as part of the research. With a normal and reduced runoff, the water in the rivers of the central part of the Sayan-Baikal Stanovoi Highlands is transparent and clean. Visible turbidity of water appears with the formation of a high water resulting from atmospheric precipitation and snowmelt. In the rivers under investigation, the turbidity at the peak of the flood or debris flow was about 7 thou g/m³, with the maximum turbidity not exceeding 25 thou g/m³ (the Slyudyanka river, 1960). The particle size of suspended material varied from silt sand to heavy sandy loam and light loam. The research has shown that suspended load, along with tractional load, plays a significant role in the formation of accumulative landforms. This is especially evident in the lower parts of the cones, where they are able to be deposited as layers reaching several meters.