Estuaries and Coasts

, Volume 30, Issue 6, pp 1106–1125

Particle trapping in stratified estuaries: Application to observations

  • David A. Jay
  • Philip M. Orton
  • Thomas Chisholm
  • Douglas J. Wilson
  • Annika M. V. Fain
Article

Abstract

Estuarine turbidity maxima (ETM) retain suspended particulate matter (SPM) through advection, settling, aggregation, and nonlinearities in bed processes, but the relative importance of these processes varies strongly between systems. Observations from two strongly advective systems (the Columbia and Fraser Rivers) are used to investigate seasonal cycles of SPM retention and the effects of very high flows. Results for the Fraser and Columbia plus literature values for 13 other estuaries illustrate the applicability of scaling parameters and the response of ETM phenomena to a range of river flow (Ur) levels and tidal forcing. The most efficient trapping (represented by Trapping EfficiencyE, the ratio of maximum ETM concentration to the source SPM concentration) occurs for low ratios of river flow to tidal current amplitude (UT), represented by low values of the Supply number Sr.E in the Columbia is found to be maximal in a null zone where advection or tidal asymmetry (represented by Advection numberA) is weak(A ∼ 0). The ratio of aggregation to disaggregation (the Floc number Θ) is maximal on neap tides, while the ratio of erosion to deposition (the Erosion number P) is maximal on spring tides. The ratio of settling velocity to vertical mixing (Rouse numberP) is relatively constant in the Columbia ETM(P ∼ 0.7), because particle settling velocity and turbulence levels adjust together. Assuming that this result applies broadly, scaling variables and data are combined to express ETM properties in terms of the friction velocity (U*),Ur, andUT, allowing a considerable simplification of the parameters used to describe ETM.

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Copyright information

© Estuarine Research Federation 2007

Authors and Affiliations

  • David A. Jay
    • 1
  • Philip M. Orton
    • 2
  • Thomas Chisholm
    • 3
  • Douglas J. Wilson
    • 3
  • Annika M. V. Fain
    • 3
  1. 1.Department of Civil and Environmental EngineeringPortland State UniversityPortland
  2. 2.Ocean and Climate Physics, LamontDoherty Earth ObservatoryColumbia UniversityPalisades
  3. 3.Department of Environmental and Biomolecular Systems, OGI School of Science and EngineeringOregon Health and Science UniversityBeaverton
  4. 4.Bonneville Power AdministrationPortland
  5. 5.Imagenex Corp.Port CoquitlamCanada
  6. 6.Philip Williams and AssociatesSan Francisco

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