Procedure Used 



7. The principal physical mechanisms which determine beach profile 

 change must be quantitatively described to model the profile response numeri- 

 cally. For this purpose it is necessary to study profile evolution under 

 varying waves, sand characteristics, and profile shape. However, to establish 

 cause and effect relationships between the governing factors and the profile 

 response, it must be possible to clearly delineate these relationships. 

 Laboratory facilities provide an environment where such investigations may be 

 carried out efficiently, while allowing for data sampling at almost any 

 spatial or temporal scale. The difficulty of transforming observations made 

 under scale distortion is eliminated if experiments are performed at the scale 

 of the prototype, i.e., at a sufficiently large scale as to satisfactorily 

 represent the interaction between fluid forces and sand grains that produces 

 significant sand transport in the field. 



8. Use of field profile data as a basis for developing a numerical 

 model is extremely difficult due to the complexity and randomness of naturally 

 occurring conditions and cost of data collection. Ultimately a numerical 

 model must be verified against field data, but, in the process of model 

 development, laboratory data can provide considerably more insight into the 

 relative influence of the factors producing the profile change. Study of 

 these individual factors implicitly assumes the validity of the superposition 

 principle for application of the model to the general case. For example, 

 examination of the effect of water level variation on profile evolution under 

 fixed incident waves isolates the influence of this factor and allows under- 

 standing of the related physical processes involved. A combination of such 

 observations constitutes the foundation for a numerical model which is used in 

 a predictive mode for varying water level and wave conditions, even though 

 these factors have been evaluated separately. Consequently, careful data 

 analysis is the basis for many assumptions and empirical relationships 

 employed in the numerical model developed here and the first logical step 

 toward understanding beach profile change by this procedure. 



9. From an engineering point of view it is of considerable importance 

 to quantify the various properties related to beach profile change. This 



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