Deposition rates and composition of overbank sediments for a steppe river with a beaded-shape channel (case study of the Kardail river, Northern Volgograd region)
Year: 2025
Type: article
Abstract: Beaded channels of small rivers, with alternating lake-like extensions and narrow channels connecting them, are widespread in the steppe zone. Nevertheless, their origin is still controversial. A version of the beaded channels formation in the steppe zone is the siltation of rivers; however the rates of sediment deposition, their composition and features of their distribution on the floodplains of beaded rivers have not been specially studied. The rates of overbank deposition were determined for the floodplain complex of the Kardail River, which has a beaded channel, using the 137Cs. The duration of inundation of different floodplain levels was estimated, and the granulometric composition of overbank deposits, suspended sediments, channel bottom sediments and soils was specified. The rate of overbank sediment deposition for the period from 1986 to 2024 grow in line with the increasing duration of floodplain inundation and amounts to no more than 1,6 mm/year for the high floodplain, 2,4–3,2 mm/year for the middle floodplain, and 10,5–13,2 mm/year for the low floodplain. The decrease in flood water rise is characteristic for all rivers in the region and leads to a decrease in the rate of sediment deposition on the middle and high floodplains. Compared with higher floodplain levels, low floodplain deposits are characterized by a higher content of plant residues and an increased proportion of silt. The finer composition of low floodplain deposits could be a result of its longer inundation, dense reeds on its surface, which slow up the flow, and the fine composition of the main sources of suspended sediments, i. e. arable soil horizon and channel bottom sediments. It was found that the rates of sediment deposition at different levels of the Kardail River floodplain correspond to those of other rivers, including those without a beaded channel morphology. The presence of the clay base under organic rich deposits within low floodplains in the narrowings of the channel indicates that the deposition of organic rich deposits is not the main cause of the formation of channel extensions, but it makes their morphology more pronounced.
Institution: Lomonosov Moscow State University
Language: English
Subfield: Ecology
Field: Environmental Science
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W4412386050