The impacts of near-bed flow characteristics on river bed sediment transport under ice-covered conditions in 2016–2021
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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Date
2022-12
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en
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15
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Journal of Hydrology, Volume 615
Abstract
Global climate change has been projected to affect hydrology, the ice-covered flow period and river morphology (including changed sediment transport conditions) in northern high-latitude regions. To understand the impact of the expected shortening of the ice-covered period on bedload transport, one needs to understand the present sediment transport in these high-latitude rivers with annually occurring ice cover. Thus, the aims are (1) to define the impacts of ice cover on near-bed flow characteristics during hydrologically varying years, and (2) to analyse the impacts of these mid-winter flow characteristics on the bed sediment transport potential. The analyses are based on Acoustic Doppler Current Profiler (ADCP: 2016–21) and Acoustic Doppler Velocimeter (ADV: 2020–21) measurements performed in mid-winter ice-covered conditions of the sandy and small (circa 20 m wide) Pulmanki River in northern Finnish Lapland. Despite the ice-covered river conditions in winter, sediment transport occurs even during these harshest mid-winter conditions. The critical velocities and shear velocities of mid-winter conditions were exceeded in winters 2016–2021, and bedload transport occurred according to bedload measurements. Three different situations occurred regarding the bed sediment transport and near-bed velocity conditions: (1) high measured mid-winter discharges indicate high velocities throughout the meander bend; (2) low measured mid-winter discharges cause low near-bed velocities throughout the meander bend; (3) winters having intermediate discharges indicate near-bed velocities and sediment transport potential being higher at the upstream inlet and apex sections of the meander bend but clearly lower downstream of the apex. The confinement by the river ice cover, i.e. bottom-fast ice, explains the velocity variation. The near-bed velocities were the highest at the upstream inlet section of a symmetrical meander bend, where the measurement cross-sections were narrower and shallower. The velocities were the lowest downstream of the apex, where the channel changed from relatively narrow to wider and deeper.Description
Funding Information: We would like to thank Dr Maria Kämäri, MSc Franziska Wolff, MSc Mariana Verdonen, MSc Tiia Tarsa and MSc Marko Kärkkäinen from the University of Eastern Finland, William Speirs from the University of Queensland (Brisbane, Australia), Dr Carlos Gonzales-Inca and MSc Jouni Salmela from the University of Turku and Dr Nikita Tananaev (Melnikov Permafrost Institute [MPI] at Yakutsk, Russia) for their valuable fieldwork assistance in 2016–2021. We also thank Marko Kärkkäinen for analysing the bedload transport amounts and grain sizes and processing the orthomosaic image from the aerial photos of February 2021. It would not have been possible to conduct the fieldwork without the drilling assistance of Ilkka Syvänperä and Esa Karpoff from the Kevo Subarctic Research Institute of University of Turku during 2016–2021. The authors have no conflicts of interest to declare. The ice-covered flow measurements were initiated under the post-doctoral research project of Dr Lotsari, funded by the Academy of Finland (ExRIVER: grant number 267345). The work for this paper was also supported financially by four other Academy of Finland funded projects (DefrostingRivers: 338480; HYDRO-RDI-Network: 337394 and 337279; InfraRiver: 296090; Green-Digi-Basin 347701). Funding was received from the Maj and Tor Nessling Foundation (ExRIVER, grant numbers: 201300067 and 201500046; Influence of river ice and fluvial processes on river environments now and in the future, grant number: 201600042) and Strategic Research Council at the Academy of Finland (Competence-Based Growth Through Integrated Disruptive Technologies of 3D Digitalization, RobotiCS, Geospatial Information and Image Processing/Computing – Point Cloud Ecosystem, grant number: 293389). The Department of Geographical and Historical Studies, University of Eastern Finland, supported the work financially. Funding was also received from the British Society for Geomorphology (research project title ʻDefrosting sedimentary systems: the impacts on the evolution and material transport of high-latitude riversʼ [registered charity number: 1054260]). Funding Information: The ice-covered flow measurements were initiated under the post-doctoral research project of Dr Lotsari, funded by the Academy of Finland (ExRIVER: grant number 267345). The work for this paper was also supported financially by four other Academy of Finland funded projects (DefrostingRivers: 338480; HYDRO-RDI-Network: 337394 and 337279; InfraRiver: 296090; Green-Digi-Basin 347701). Funding was received from the Maj and Tor Nessling Foundation (ExRIVER, grant numbers: 201300067 and 201500046; Influence of river ice and fluvial processes on river environments now and in the future, grant number: 201600042) and Strategic Research Council at the Academy of Finland (Competence-Based Growth Through Integrated Disruptive Technologies of 3D Digitalization, RobotiCS, Geospatial Information and Image Processing/Computing – Point Cloud Ecosystem, grant number: 293389). The Department of Geographical and Historical Studies, University of Eastern Finland, supported the work financially. Funding was also received from the British Society for Geomorphology (research project title ʻDefrosting sedimentary systems: the impacts on the evolution and material transport of high-latitude riversʼ [registered charity number: 1054260]). Publisher Copyright: © 2022 The Authors
Keywords
Finland, Ice-covered flow, Near-bed velocity, Sediment transport, Subarctic, Time series analysis
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Citation
Lotsari, E, Lintunen, K, Kasvi, E, Alho, P & Blåfield, L 2022, ' The impacts of near-bed flow characteristics on river bed sediment transport under ice-covered conditions in 2016–2021 ', Journal of Hydrology, vol. 615, 128610 . https://doi.org/10.1016/j.jhydrol.2022.128610