36 



gravitational attraction and centrifugal reaction for the system comprising 

 the earth, the moon and the sun. This theory has been summarized by Dean 

 (1966) ; it highlights the role of the basic forces in generating periodic 

 oscillations of the water surface, and their dependence on such factors as 

 the latitude, the declination of moon and the relative effects of the moon 

 and the sun . 



During the 1920s, Proudman (see, for example, Proudman, 1925) 

 published a series of articles in which he investigated various aspects of 

 tidal motion including the Coriolis effect due to earth's rotation. The 

 significant advance made relative to the equilibrium theory was accounting 

 for the actual motion of water particles on the rotating earth. Computer 

 technology has now made it feasible to simulate tidal motion over entire 

 oceanic masses. Early computations were based on solutions of Laplace's 

 tidal equations (LTE) . A review of numerical models of the sixties and the 

 seventies has been provided by Hendershott (1977). Subsequently, more 

 general forms of the Navier-Stokes equations of motion have been solved. A 

 recent review of solutions of these ocean tidal equations (OTE) has been 

 provided by Schwiderski (1986) . 



Tides in the nearshore environment are considerably influenced by 

 winds, waves, bottom topography as well as temperature- and 

 salinity- induced stratification. Where astronomical tides are small, e.g., 

 along U.S. Gulf coast, non- tidal forcing often assumes overwhelming 

 significance and modeling of a purely deterministic nature becomes 

 difficult. Physical considerations along these lines have been reviewed by 

 Csanady (1984) . 



Proudman' s contributions also included considerations for tidal 

 motions in channels of various cross-sectional shapes, and the effect of 

 coastal configuration on offshore tidal features. A good review of simple 

 analytic approaches for tidal propagation in estuaries, without and with 

 bottom frictional effects, has been presented by Ippen and Harleman (1966). 

 For the fundamentals on numerical methods for estuarine hydrodynamics, the 

 works of Dronkers (1964) and Abbott (1979) may be cited. Nihoul and Jamart 

 (1987) have edited a series of contributions on the state-of-the-art 

 modeling techniques of marine and estuarine hydrodynamics using 

 three-dimensional numerical approaches. 



