The negative role of turbulence in estuarine mass transport

Richard A Nunes Vaz, Geoffrey W Lennon, Jayantha R de Silva Samarasinghe

Research output: Contribution to journalArticlepeer-review

95 Citations (Scopus)

Abstract

It is competition between the various stratifying and mixing influences which determines the character of stratification in an estuary. Borrowing concepts which have been successfully applied to the discussion of stratification in shelf seas, a quantitative basis for determining the potential energy associated with vertical structure in estuaries is derived. The formulation, along similar lines to that of Bowden (1981), provides a simple but comprehensive method of incorporating many relevant stratifying and mixing influences in a given problem, and is also shown to be capable of rearrangement into forms akin to the estuarine Richardson number which is commonly found in discussions of estuarine statification. The paper argues, based on a survey of the literature, that in wide, relatively well-mixed estuaries, the greatest longitudinal mass flux occurs at times when stratification is most developed, that is, when the turbulent kinetic energy in the water column is at a minimum. Modulation of turbulence, principally at various tidal frequencies, causes a pulsing of the mass flux in which the contribution of each pulse increases non-linearly as the period of the modulation increases. Some, possibly significant, changes to the state of stratification and to the corresponding mass transport may occur in association with slack water periods. However, the spring-neap cycle is proposed to have a far greater influence on stratification, mass transport and the long-term mass balance in estuaries, and recent observational studies lend support to this position.

Original languageEnglish
Pages (from-to)361-377
Number of pages17
JournalEstuarine, Coastal and Shelf Science
Volume28
Issue number4
DOIs
Publication statusPublished - Apr 1989

Keywords

  • density current
  • dispersion
  • estuaries
  • mass transport
  • review article
  • stratification
  • tidal cycles
  • turbulence

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