Sensitivity of tidal characteristics in double inlet systems to momentum dissipation on tidal flats: a perturbation analysis

Tjebbe M. Hepkema, Huib E. de Swart, Antonios Zagaris, Matias Duran–Matute

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

In a tidal channel with adjacent tidal flats, along–channel momentum is dissipated on the flats during rising tides. This leads to a sink of along–channel momentum. Using a perturbative method, it is shown that the momentum sink slightly reduces the M2 amplitude of both the sea surface elevation and current velocity and favours flood dominant tides. These changes in tidal characteristics (phase and amplitude of sea surface elevations and currents) are noticeable if widths of tidal flats are at least of the same order as the channel width, and amplitudes and gradients of along–channel velocity are large. The M2 amplitudes are reduced because stagnant water flows from the flats into the channel, thereby slowing down the current. The M4 amplitudes and phases change because the momentum sink acts as an advective term during the fall of the tide, such a term generates flood dominant currents. For a prototype embayment that resembles the Marsdiep–Vlie double–inlet system of the Western Wadden Sea, it is found that for both the sea surface elevation and current velocity, including the momentum sink, lead to a decrease of approximately 2% in M2 amplitudes and an increase of approximately 25% in M4 amplitudes. As a result, the net import of coarse sediment is increased by approximately 35%, while the transport of fine sediment is hardly influenced by the momentum sink. For the Marsdiep–Vlie system, the M2 sea surface amplitude obtained from the idealised model is similar to that computed with a realistic three–dimensional numerical model whilst the comparison with regard to M4 improves if momentum sink is accounted for.

LanguageEnglish
Pages439-455
Number of pages17
JournalOcean Dynamics
Volume68
Issue number4-5
DOIs
StatePublished - Apr 2018

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tidal flat
dissipation
momentum
perturbation
sea surface
tide
tidal channel
analysis
sediment
import
water flow

Keywords

  • Marsdiep–Vlie system
  • Momentum sink
  • Overtides
  • Perturbation analysis
  • Sediment transport

Cite this

@article{490e8efa3e094877b5dbb159deebaa17,
title = "Sensitivity of tidal characteristics in double inlet systems to momentum dissipation on tidal flats: a perturbation analysis",
abstract = "In a tidal channel with adjacent tidal flats, along–channel momentum is dissipated on the flats during rising tides. This leads to a sink of along–channel momentum. Using a perturbative method, it is shown that the momentum sink slightly reduces the M2 amplitude of both the sea surface elevation and current velocity and favours flood dominant tides. These changes in tidal characteristics (phase and amplitude of sea surface elevations and currents) are noticeable if widths of tidal flats are at least of the same order as the channel width, and amplitudes and gradients of along–channel velocity are large. The M2 amplitudes are reduced because stagnant water flows from the flats into the channel, thereby slowing down the current. The M4 amplitudes and phases change because the momentum sink acts as an advective term during the fall of the tide, such a term generates flood dominant currents. For a prototype embayment that resembles the Marsdiep–Vlie double–inlet system of the Western Wadden Sea, it is found that for both the sea surface elevation and current velocity, including the momentum sink, lead to a decrease of approximately 2{\%} in M2 amplitudes and an increase of approximately 25{\%} in M4 amplitudes. As a result, the net import of coarse sediment is increased by approximately 35{\%}, while the transport of fine sediment is hardly influenced by the momentum sink. For the Marsdiep–Vlie system, the M2 sea surface amplitude obtained from the idealised model is similar to that computed with a realistic three–dimensional numerical model whilst the comparison with regard to M4 improves if momentum sink is accounted for.",
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Sensitivity of tidal characteristics in double inlet systems to momentum dissipation on tidal flats : a perturbation analysis. / Hepkema, Tjebbe M.; de Swart, Huib E.; Zagaris, Antonios; Duran–Matute, Matias.

In: Ocean Dynamics, Vol. 68, No. 4-5, 04.2018, p. 439-455.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Sensitivity of tidal characteristics in double inlet systems to momentum dissipation on tidal flats

T2 - Ocean Dynamics

AU - Hepkema,Tjebbe M.

AU - de Swart,Huib E.

AU - Zagaris,Antonios

AU - Duran–Matute,Matias

PY - 2018/4

Y1 - 2018/4

N2 - In a tidal channel with adjacent tidal flats, along–channel momentum is dissipated on the flats during rising tides. This leads to a sink of along–channel momentum. Using a perturbative method, it is shown that the momentum sink slightly reduces the M2 amplitude of both the sea surface elevation and current velocity and favours flood dominant tides. These changes in tidal characteristics (phase and amplitude of sea surface elevations and currents) are noticeable if widths of tidal flats are at least of the same order as the channel width, and amplitudes and gradients of along–channel velocity are large. The M2 amplitudes are reduced because stagnant water flows from the flats into the channel, thereby slowing down the current. The M4 amplitudes and phases change because the momentum sink acts as an advective term during the fall of the tide, such a term generates flood dominant currents. For a prototype embayment that resembles the Marsdiep–Vlie double–inlet system of the Western Wadden Sea, it is found that for both the sea surface elevation and current velocity, including the momentum sink, lead to a decrease of approximately 2% in M2 amplitudes and an increase of approximately 25% in M4 amplitudes. As a result, the net import of coarse sediment is increased by approximately 35%, while the transport of fine sediment is hardly influenced by the momentum sink. For the Marsdiep–Vlie system, the M2 sea surface amplitude obtained from the idealised model is similar to that computed with a realistic three–dimensional numerical model whilst the comparison with regard to M4 improves if momentum sink is accounted for.

AB - In a tidal channel with adjacent tidal flats, along–channel momentum is dissipated on the flats during rising tides. This leads to a sink of along–channel momentum. Using a perturbative method, it is shown that the momentum sink slightly reduces the M2 amplitude of both the sea surface elevation and current velocity and favours flood dominant tides. These changes in tidal characteristics (phase and amplitude of sea surface elevations and currents) are noticeable if widths of tidal flats are at least of the same order as the channel width, and amplitudes and gradients of along–channel velocity are large. The M2 amplitudes are reduced because stagnant water flows from the flats into the channel, thereby slowing down the current. The M4 amplitudes and phases change because the momentum sink acts as an advective term during the fall of the tide, such a term generates flood dominant currents. For a prototype embayment that resembles the Marsdiep–Vlie double–inlet system of the Western Wadden Sea, it is found that for both the sea surface elevation and current velocity, including the momentum sink, lead to a decrease of approximately 2% in M2 amplitudes and an increase of approximately 25% in M4 amplitudes. As a result, the net import of coarse sediment is increased by approximately 35%, while the transport of fine sediment is hardly influenced by the momentum sink. For the Marsdiep–Vlie system, the M2 sea surface amplitude obtained from the idealised model is similar to that computed with a realistic three–dimensional numerical model whilst the comparison with regard to M4 improves if momentum sink is accounted for.

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KW - Momentum sink

KW - Overtides

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SP - 439

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JO - Ocean Dynamics

JF - Ocean Dynamics

SN - 1616-7341

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ER -