Basic Characteristics of Tides and Tidal Propagation

The basic theory regarding astronomical tides has been dealt with in books written by Defant, Neumann and Pierson and Macmillan and other specialised texts. This chapter emphases those aspects of tides which are of interest to engineers dealing with tidal and coastal engineering problems. The gravitational attraction of the moon and sun on the earth and the equal and opposite centrifugal forces are the main forces responsible for the generation of tides. The occurrence of tides can be explained from the law of gravitational attraction, i.e., the gravitational force varies inversely as the square of the distance between the two objects. The rise and fall of water in the oceans is propagated as a shallow-water wave, since the wavelength is large compared to the depth of water. For automatic recording of the continuous movement of the water level one can adopt either the analogue system or the digital system.