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Observations of residual exchange flows at the entrance to four subtropical estuaries, two of them semiarid, indicate that these flows are mainly tidally driven, as they compare favorably with theoretical patterns of tidal residual flows. In every estuary examined, the tidal behavior was that of a standing or near-standing wave, i.e., tidal elevation and tidal currents were nearly in quadrature. The pattern of exchange flow that persisted at every estuary exhibited inflow in the channel and outflow over the shoals. Curiously, but also fortuitously, this pattern coincides with the exchange pattern driven by density gradients in other estuaries. The tidal stresses and the residual elevation slopes should be the dominant mechanisms that drive such tidal residual pattern because the Stokes transport mechanism is negligible for standing or near-standing waves. Time series measurements from the semiarid estuaries showed fortnightly modulation of the residual flow by tidal forcing in such a way that the strongest net exchange flows developed with the largest tidal distortions, i.e., during spring tides. This modulation is opposite to the modulation that typically results in temperate estuaries, where the strongest net exchange flows tend to develop during neap tides. The fortnightly modulation on tidal residual currents could be inferred from previous theoretical results because residual currents arise from tidal distortions but is made explicit in this study. The findings advanced herein should allow the drawing of generalities about exchange flow patterns in subtropical estuaries where residual flows are mainly driven by tides. [ABSTRACT FROM AUTHOR]

The article discusses the highlights of the 14th International Biennial Conference on Physics of Estuaries and Coastal Seas (PECS 2008) which was held in Liverpool, England from August 15-29. The conference is chaired by Charitha Pattiaratchi and adopted the theme on process studies in the pre-operational era. The sponsors of the conference, including the Proudman Oceanographic Laboratory, the UK Environment Agency and the Explorocean Ltd., are mentioned.

This article reflects on the 12th International Biennial Conference on Physics of Estuaries and Coastal Seas (PECS) held in Mérida, México from October 19 to 22, 2004. PECS philosophy has been to stimulate the cooperation between the coastal engineers and coastal oceanographers. The topic of PECS 2004 was Hydrodynamics and Morphodynamics in Estuaries and Coastal Seas, including estuarine hydrodynamics, coastal hydrodynamics, coastal transport and morphodynamics.