Dynamics Of Motion In Estuaries And Other Coastal Water Bodies

In this evaluation of studies of the dynamics of motion in estuaries and other coastal bodies of water made by U.S. investigators during the period 1975 through 1978, we have chosen to treat four subject areas in which we feel there have been significant advances. Within each of these areas we have included those papers which we feel have contributed most to the advances as we perceive them. This paper is thus a selective review of research in the U.S. on the dynamics of motion in estuaries and other coastal water bodies during the past four years, and is not intended to be a comprehensive review of all works for this period. The four areas of research to be reviewed here are: (1) The variability in time and space of the non-tidal motion in estuaries. There has been a large increase in the deployment of in situ recording current meters in moored arrays in estuaries over the last decade. Some of these deployments covered periods from several weeks to several months, and at least two single station vertical arrays provided almost continuous data for about 12 months. Analysis of the data from these deployments have provided a rapidly increasing appreciation of the variability of estuarine circulation. (2) Non-local forcing of non-tidal variations in water level and motion in estuaries and other coastal water bodies. The recognition of the importance of events on the shelf in driving the motion within estuaries is a unique contribution of the past four years. Of course, large events, such as storm surges associated with hurricanes, had long been recognized as contributing to departures in the characteristic estuarine flow pattern, but it has only been recently recognized that variations in the water surface elevation and in the volume transport having periodicities of 3 to 20 days can be driven by events outside the estuary. (3) The effects of the non-linear field acceleration terms on the tidal averaged dynamics of estuarine circulation. When the equations of motion are averaged over a tidal period, there arise non-linear momentum flux terms involving the purely oscillatory, zero-centered, tidal velocities. A number of studies in the last four years have demonstrated that these terms can result in residual (i.e., tidal averaged) currents in estuaries and other coastal water bodies. To a large extent these studies were stimulated by a paper on the Stokes velocity resulting from oscillatory motion written by Longuet-Higgins (1969) nearly a decade ago. However, the application of the concepts in that study to tidal motion in estuaries has occurred only recently. (4) Numerical modeling of storm surges in estuaries and other coastal bodies of water. The modeling of storm surges on the open coast has a long history, particularly in Europe. The extension of this modeling to estuaries, bays and sounds is a more recent development, though certainly pre-dating the past four years. However, significant advances in storm surge modeling of estuaries has occurred in this period. These models have in some cases also been applied to tidal motion and non-storm surge tidal averaged circulation in estuaries.