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Open AccessArticle

Macro-Turbulent Flow and Its Impacts on Sediment Transport Potential of a Subarctic River during Ice-Covered and Open-Channel Conditions

1
Department of Geographical and Historical Studies, University of Eastern Finland, Yliopistokatu 2, P.O. Box 111, FI-80101 Joensuu, Finland
2
Department of Geography and Geology, University of Turku, Turun yliopisto, FI-20014 Turku, Finland
3
Section 4.6 Geomorphology, German Research Centre for Geosciences GFZ Potsdam, D-14473 Potsdam, Germany
4
Finnish Environment Institute, Latokartanonkaari 11, FI-00790 Helsinki, Finland
5
Finnish Geospatial Research Institute, National Land Survey of Finland, Geodeetinrinne 2, FI-02430 Masala, Finland
6
Turku University of Applied Sciences, Joukahaisenkatu 3, FI-20520 Turku, Finland
*
Author to whom correspondence should be addressed.
Water 2020, 12(7), 1874; https://doi.org/10.3390/w12071874
Received: 28 May 2020 / Revised: 22 June 2020 / Accepted: 25 June 2020 / Published: 30 June 2020
Macro-turbulent flows (i.e., coherent flow structures reaching through the whole water column), have not been studied widely in northern seasonally frozen rivers during both open-channel and ice-covered flow conditions. Thus, we aim: (1) to detect and compare the macro-turbulent flow, both at open-channel and ice-covered flow conditions; (2) to explore spatial variation of macro-turbulent flow characteristics within a meander bend; and (3) to detect the effects of near-bed layer velocity fluctuation on bedload transport during differing overall flow conditions. The analyses are based on 5–10 min-long acoustic Doppler current profiler (ADCP) measurements from a subarctic river. The ice-covered low flow, and open-channel higher and lower flow conditions were measured over the period of 2016 to 2020. This study found that macro-turbulent flow existed at all measurement locations under both open-channel and ice-covered flow conditions. Macro-turbulent flow was most consistent and obvious in the streamwise velocity component, and in particular at the inlet and outlet of the investigated meander bend. During all seasons, the near-bed velocities consistently exceeded the sufficient amount for sediment transport. At inlet and outlet areas, the greatest near-bed velocity fluctuation across the critical threshold for sediment transport coincided with the measurement times having frequent macro-turbulent flow. View Full-Text
Keywords: macro-turbulence; velocity; ADCP; cluster analysis; ice-covered flow; open-channel flow; subarctic macro-turbulence; velocity; ADCP; cluster analysis; ice-covered flow; open-channel flow; subarctic
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    Doi: 10.5281/zenodo.3855035
    Description: ADCP data of ice-covered and open-channel (macro-turbulent) flow, Pulmanki River, 2016-2020
MDPI and ACS Style

Lotsari, E.; Dietze, M.; Kämäri, M.; Alho, P.; Kasvi, E. Macro-Turbulent Flow and Its Impacts on Sediment Transport Potential of a Subarctic River during Ice-Covered and Open-Channel Conditions. Water 2020, 12, 1874.

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