Turbulence and turbulent flux events in tidal bores: case study of the undular tidal bore of the Garonne River

Leng, Xinqian; Chanson, Hubert; Reungoat, David

doi:10.1007/s10652-017-9561-9

Cited by 14 publications

(8 citation statements)

References 34 publications

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“…8. Current results showed a strong link between turbulent bursting events and suspended sediment concentrations, as previously reported in the field (Amirshahi et al, 2018;Leng et al, 2018).…”

Section: Basic Observationssupporting

confidence: 89%

Turbulence and suspended sediment processes in the Garonne River tidal bore in November 2016

Reungoat

Leng

Chanson

2019

International Journal of Sediment Research

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A tidal bore is a water discontinuity at the leading edge of a flood tide wave in estuaries with a large tidal range and funneling topography. New measurements were done in the Garonne River tidal bore on 14-15 November 2016, at a site previously investigated between 2010 and 2015. The data focused on long, continuous, high-frequency records of instantaneous velocity and suspended sediment concentration (SSC) estimate for several hours during the late ebb, tidal bore passage and flood tide. The bore passage drastically modified the flow field, with very intense turbulent and sediment mixing. This was evidenced with large and rapid fluctuations of both velocity and Reynolds stress, as well as large SSCs during the flood tide. Granulometry data indicated larger grain sizes of suspended sediment in water samples compared to sediment bed material, with a broader distribution, shortly after the tidal bore. The tidal bore induced a sudden suspended sediment flux reversal and a large increase in suspended sediment flux magnitude. The time-variations of turbulent velocity and suspended sediment properties indicated large fluctuations throughout the entire data set. The ratio of integral time scales of SSC to velocity in the x-direction was on

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Section: Basic Observationssupporting

confidence: 89%

Turbulence and suspended sediment processes in the Garonne River tidal bore in November 2016

Reungoat

Leng

Chanson

2019

International Journal of Sediment Research

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“…Furthermore, soft-sediment deformation structures are much more common in the Mont Saint Michel Bay, Turnagain Arm and Qiantang systems than in the present study area. At the other end of the spectrum, there is an area in the Garonne River, France, that has been the site of several studies of tidal-bore dynamics (Chanson et al, 2011;Reungoat et al, 2014Reungoat et al, , 2017Reungoat et al, , 2018Keevil et al, 2015;Leng et al, 2018). There, the water depth at low tide (i.e.…”

Section: Variability Of Tidal-bore Deposits: Is a Single Universal Facies Model Possible?mentioning

confidence: 99%

Sedimentation on high‐energy sand flats in the Bay of Fundy: The record of tidal‐bore activity and deposition from high‐concentration suspensions of sand

Dalrymple

2021

Sedimentology

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The Cobequid Bay -Salmon River estuary, Bay of Fundy, does not possess particularly large tidal bores (maximum ca 30 cm). Nevertheless, detailed logging of 13 peels made from cores spread throughout the entire area influenced by tidal bores indicates that inferred tidal-bore deposits comprise approximately 15% of the deposits in the upper-flow-regime sand flats in the inner part of the estuary, averaging more than 10 tidal-bore layers per metre of core. A landward increase in tidal-bore height is accompanied by an increase in the number and thickness of the tidal-bore layers. The deposit of a single tidal bore begins with structureless sand (from <1 cm to >10 cm thick) that can be gradationally overlain by sand with indistinct parallel lamination, which in turn passes upward into the well-defined parallel lamination that is the dominant sedimentary structure in these sand-flat deposits. The bases of the structureless layers range from prominently erosional to passively draping over the ripples formed during the preceding ebb tide. The structureless and indistinctly laminated layers are interpreted to be the deposit of boregenerated hyperconcentrated suspensions of sand that have similarities with turbidity currents in which near-bed turbulence is extinguished or damped. The tidal-bore Froude number (Fr tb ), which determines the nature of the tidal bore, together with the height of the tidal bore, influences the amount of sand in suspension, and presumably also controls the nature of the deposits. Tidal bores with high Froude numbers (Fr tb = 2 to 3) that are breaking create deposits that are analogous to the deposits of high-concentration turbidity currents; most bore deposits documented to date from other ancient and modern settings are of this high-energy type. Tidal bores that are closer to the lower limit of bore occurrence (Fr tb = 1) generate deposits that will be difficult to distinguish from the background sedimentation.Keywords Bay of Fundy, high-concentration turbidity currents, parallel lamination, tidal-bore deposits, tidal bores, tide-dominated estuary, upper flow regime sedimentation. Thus, their deposits might be common in tidedominated estuaries and deltas, wherever the incoming tidal wave becomes strongly asymmetrical, and especially in areas with a flood-tide dominance and at times with low river flow.

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“…Turbulent event analyses have been successfully applied to a number of geophysical applications assuming quasi-steady flow conditions (Narasimha et al 2007, Trevethan andChanson 2010). Their application to transient flow situations is rarer (Leng et al 2018).…”

Section: Introductionmentioning

confidence: 99%

“…In this study, a turbulent event analysis was developed for the highly-unsteady rapidly-varied surge flow following Leng et al (2018) and applied to a breaking bore. The analysis was based upon the definition of turbulent bursting events in terms of the instantaneous relative turbulent flux.…”

Section: Introductionmentioning

confidence: 99%

Turbulent Mixing and Turbulent Events in Breaking Bores

Shi¹,

Leng²,

Chanson³

2019

38th IAHR World Congress - "Water: Connecting the World"

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A breaking tidal bore is a highly turbulent transient process that may affect the natural estuarine system. Like many natural process flows, the tidal bore flow motion is dominated by coherent structure activities and turbulent events, with significant impact in terms of sediment processes. Herein an unsteady turbulent event analysis was developed for highly-unsteady rapidly-varied breaking bore flows. New experimental data were collected in a large size facility under controlled flow conditions. The data analysis was based upon basic concepts, in which turbulent bursting events were defined in terms of the instantaneous relative turbulent flux, and applied to the rapidly-varied highly-unsteady bore motion. The instantaneous three-dimensional velocities were recorded using an Acoustic Doppler Velocimetry. Rapid longitudinal deceleration, transient recirculation and large velocity fluctuations were observed during the bore passage, especially more intensive next to the sidewall. A turbulent event analysis was performed in the transient flow. The threshold constant k =1 was obtained from a sensitivity analysis. The unsteady turbulent event results highlighted an intense bursting process during the flow deceleration, in terms of the relatively large event duration, event amplitude and relative magnitude compared with the early flood flow phase. The unsteady event amplitude and relative magnitude exhibited a quasi-symmetrical distribution about the zero amplitude. The majority of turbulent events lasted between 0.005 s to 0.06 s. Overall, the results showed that the turbulent event analysis provided valuable quantitative details into the turbulent bursts that are responsible for major mixing and sedimentary processes.

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Turbulence and turbulent flux events in tidal bores: case study of the undular tidal bore of the Garonne River

Cited by 14 publications

References 34 publications

Turbulence and suspended sediment processes in the Garonne River tidal bore in November 2016

Turbulence and suspended sediment processes in the Garonne River tidal bore in November 2016

Sedimentation on high‐energy sand flats in the Bay of Fundy: The record of tidal‐bore activity and deposition from high‐concentration suspensions of sand

Turbulent Mixing and Turbulent Events in Breaking Bores

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