Estuaries and coastal

Surface waters reach the ocean via the coastal or estuarine environment, where the transport of pollutants is influenced by natural bathymetry, tidal and surface waves. This results in a complex time-varying flow field. The change in depth introduces changes in velocity, increasing mixing.

Wallingford Coastal Research Facility.
Wallingford Coastal Research Facility.
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This complexity is further amplified in estuaries by density variations caused by the mixing of salt and fresh water. The density difference can introduce secondary circulations, increasing cross-sectional mixing. In ebb tides, the vertical turbulent transport of momentum is inhibited, reducing transport, while the movement of flood tides increases secondary recirculation.

To-date, there have been few attempts to measure transverse mixing in estuaries, eg, Guymer and West (1992). Such measurements are needed for modelling and management of estuarine waters, to improve water quality in the nearshore zone.

In particular, mixing in estuarine waters is of interest to limit saline intrusion into water intakes, reduce groundwater contamination and reduce the consequences of dredging on both nutrients and pollutants.

Breaking waves enhance near-shore mixing.
Breaking waves enhance near-shore mixing.

Relevant articles

  • Guymer, I. and West, J. R. (1992). . Journal of Hydraulic Engineering, 118(5), 718-734.
  • Pearson, J. M., Guymer, I., West, J. R. and Coates, L. (2002). . Journal of Waterway, Port, Coastal and Ocean Engineering, 128(1), 10-20.

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