Turbulence and Particle Deposition Under Steady Flow Along a Submerged Seagrass Meadow

Journal of Geophysical Research Oceans, Journal Year: 2020, Volume and Issue: 125(5)

Published: April 6, 2020

Abstract Seagrass meadows can retain fine particles, improving water clarity and promoting carbon sequestration. Laboratory experiments were conducted to investigate the influence of velocity meadow density on retention particles within a meadow. Vertical profiles turbulent kinetic energy ( TKE ) measured along model The net deposition was using microscope slides positioned inside outside correlated with evolution At leading edge, decreased over distance L r , relative bare bed, which associated region vertical updraft elevated . Net increased from decrease in In some cases, distinct peak observed at p minimum Both increasing density. Deposition fully developed decreasing stem channel velocity, for lowest highest less than that channel. Diminished linked resuspension driven by stem‐generated turbulence. A canopy‐averaged validated used explore range field conditions would be reduced, support accumulation organic material

Language: Английский

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Impact of an emergent model vegetation patch on flow adjustment and velocity

Proceedings of the Institution of Civil Engineers - Water Management, Journal Year: 2021, Volume and Issue: 175(2), P. 55 - 66

Published: July 6, 2021

This study achieved three goals to clarify the impact of a vegetation patch on flow adjustment and velocity. First, valid equation for interior distance (L d ) inside model was developed wide range velocities depths. Second, minimum beyond which resuspension fine sediment is suppressed min found be related position at local velocity decreases threshold generating stem-scale turbulence. L primarily depends blockage (C ab) stem diameter (d): shorter result larger C ab smaller d. An formulated estimating . Third, fully region > x ), an estimate increase in mean bare channel relative overall For < 2, this fraction controlled by both density (ad) (b/B) whereas, only b/B. A suggestion choosing size future research projects presented.

Language: Английский

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Drag variations, tidal asymmetry and tidal range changes in a mangrove creek system

Earth Surface Processes and Landforms, Journal Year: 2021, Volume and Issue: 46(9), P. 1828 - 1846

Published: April 1, 2021

Abstract Aboveground root structures enhance drag on tidal currents in intertidal mangrove forests, whereas the creeks dissecting such forests provide low‐resistance conduits for flows. Here, observations from an established forest Whitianga Estuary, Aotearoa New Zealand, are used to investigate variability of experienced by flows a creek system and subsequent effects asymmetries ranges. Tidal flow speed maxima occurred at overbank water levels during sheet stage rising tides, but below bank (the stage) falling tides. Inferred bulk coefficients were greater than stage, linearly correlated with stations adjacent forest. Although associated larger coefficients, had increasingly longer duration tides towards back forest, we observed ebb‐dominant asymmetry that declined inland creek. Conversely, speeds within consistently flood‐dominant, accordance smaller Along full length system, high‐water lowered up 12 cm/km 36 Creek bed roughness deeper parts was much hydraulic sediment. For accurate simulations landscape‐scale feedbacks between incorporating both direct indirect contributions vegetated platform is essential. These findings show interaction key driver as well attenuation conditions.

Language: Английский

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Microplastic trapping efficiency and hydrodynamics in model coral reefs: A physical experimental investigation

Environmental Pollution, Journal Year: 2023, Volume and Issue: 342, P. 123094 - 123094

Published: Dec. 8, 2023

Coastal ecosystems, such as coral reefs, are vulnerable to microplastic pollution input from proximal riverine and shoreline sources. However, deposition, retention, transport processes largely unevaluated, especially in relation hydrodynamics. For the first time, we experimentally investigate retention of biofilmed by branching 3D printed corals (staghorn Acropora genus) under various unidirectional flows (U = {0.15, 0.20, 0.25, 0.30} ms−1) canopy densities (15 48 m−2). These variables found drive trapping efficiency, with 79–98% microplastics retained canopies across experimental duration at high flow velocities 0.25–0.30 ms−1), compared 10–13% for bare bed, denser retaining only 15% more than sparse highest conditions 0.30 ms−1). Three fundamental mechanisms were identified: (a) particle interception, (b) settlement on branches or within coral, (c) accumulation downstream wake region coral. Corresponding hydrodynamics reveal that spatial distribution is modulated energy-dissipative effects due flow-structure interactions reducing in-canopy generating localised turbulence. The wider ecological implications systems discussed light findings, particularly terms concentrations locations plastic accumulation.

Language: Английский

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Flow and Turbulence Due To Wood Contribute to Declogging of Gravel Bed

Geophysical Research Letters, Journal Year: 2024, Volume and Issue: 51(2)

Published: Jan. 21, 2024

Abstract The placement of wood in rivers is a common restoration method used to locally affect hydraulic and morphologic conditions create habitat. Laboratory experiments demonstrated that placements can also promote surface declogging, is, removal fine sediment from gravel bed, thereby restoring spawning grounds for fish. Logs different size submergence level were placed on bed clogged with fines. Surface declogging was observed regions elevated turbulence the log wake velocity adjacent log. A criteria identified based modified non‐dimensional Shields parameter combining mean turbulent at bed. footprint declogged scaled dimensions. Emergent logs produced larger compared submerged same length, due their stronger influence flow field. shown prevent clogging over similar areas.

Language: Английский

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