used in the model. Therefore, as knowledge of cross-shore fluid flows and 

 sediment transport improves, the model is sufficiently general and flexible to 

 allow inclusion of these advances to supplement the transport rate formulas 

 developed in this study. Under the assumption of linear superposition, 

 contributions from driving forces other than short-period breaking waves can 

 be added if the transport rate relations are known. Examples for future 

 inclusion would be transport by undertow and long-period wave motions. 



381. In Part IV, a clear connection was found between macrof eatures of 

 the beach profile and wave and sand characteristics. Reliable prediction of 

 the net cross -shore sand transport rate distribution on the spatial scale of 

 meters and time frame of minutes was demonstrated in Part V. Thus, all 

 preparatory work supports the feasibility of developing a predictive engineer- 

 ing numerical model for simulating macroscale changes in the beach profile. 



Methodology 



382. At the present state of knowledge, it is clear that any type of 

 numerical model of beach profile change to be used in engineering practice 

 must be based on semi-empirical relationships derived from measurements. The 

 model presented here was developed using data from experiments carried out in 

 LWTs involving waves of prototype size. 



383. Dally (1980) and Birkemeier et al . (1987) presented criteria to 

 judge the suitability of a numerical model of beach profile change. In the 

 present work, the following properties were considered to be fundamental. The 

 model should: 



a. Accurately simulate time evolution of a profile of arbitrary 

 shape subjected to changes in water level and incident wave 

 parameters . 



b. Calculate an equilibrium configuration if all model parameters 

 and input values are held constant. 



c. Simulate formation and movement of main morphologic profile 

 features such as bars and berms . 



d. Reproduce erosional and accretionary beach change. 



e. Be verified for a wide range of realistic conditions. 



384. A short description of the capabilities of existing numerical 

 models is contained in the literature review in Part II. Of the various 



156 



