17. The break point is located where the maximum particle velocity of 

 the wave exceeds the wave celerity and the front face of the wave becomes 

 vertical. As a wave breaks, the crest falls over into the base of the wave 

 accompanied by large amount of energy dissipation. If the breaking waves are 

 of the plunging type, the point of impingement is easily recognized and 

 denoted as the plunge point. For spilling breakers, however, the plunge point 

 concept is not commonly used, but such a point could be defined using the 

 location of maximum energy dissipation. This definition is in accordance with 

 the conditions prevailing at the plunge point for a plunging breaker. 



18. A beach profile exposed to constant wave and water level conditions 

 over a sufficiently long time interval, as can be done in the laboratory, will 

 attain a fairly stable shape known as the equilibrium profile. On a beach in 

 nature, where complex wave and water level variations exist, an equilibrixom 

 profile may never develop or, if so, only for a short time before the waves or 

 water level again change. However, the equilibrium concept remains useful 

 since it provides information on the amount of sand that has to be redistrib- 

 uted within the profile to attain the natural shape for a specific set of wave 

 conditions. The equilibrium profile is in general considered to be a function 

 of sand and wave characteristics. 



Organization of This Report 



19. Part I is an introduction and gives a statement of the problem and 

 objectives of the investigation. Part II reviews the literature of beach 

 profile change, covering laboratory, field, and theoretical studies, and ends 

 with a synthesis of results considered to be of particular relevance to the 

 present investigation. Since the approach taken relies extensively on 

 measurements, the data sets used are discussed in detail in Part III. 



20. The main portion of the original work in this investigation was 

 performed in a logical progression of three substudies. The first substudy, 

 presented in Part IV, quantifies the morphology of the beach profile and the 

 dynamics of its change under wave action. Based on these results, general 

 features of cross -shore transport and empirically-based transport rate 

 formulas needed for the development of the predictive numerical model are 



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