PART III: PREDICTIVE MODELS OF PROFILE CHANGE AND DUNE EROSION 



44. This section identifies the criteria by which the applicability 

 and suitability of a numerical model for simulating profile change can be 

 judged. The criteria define the properties of an ideal model, one that 

 neither presently exists nor is expected to be developed in the immediate 

 future. The list is given to provide a standard or checklist with which 

 existing profile change models can be evaluated. 



45. A dune erosion model need not possess all the properties of a 

 profile change model because a dune erosion model is aimed at simulating an 

 extreme erosion event. The process of beach recovery is assumed to be 

 secondary and can be neglected at the first stage of dune erosion model 

 development. Moreover, as discussed earlier, the accuracy requirements of a 

 model for V-zone determination are much less restrictive than those required 

 for an empirical process-response numerical sediment transport model. 

 Therefore, a subset of the criteria defining the properties of an ideal beach 

 profile model is identified for use in evaluating dune erosion numerical 

 models . 



46. Several of the more recent theoretical models of cross-shore 

 sediment transport and beach profile change are briefly described. Then a 

 more detailed evaluation of one of the models is made from the perspective of 

 potential use as a dune erosion model. 



Required Characteristics of Beach Profile Change Models 



47. An attempt was made to compile a complete list of properties and 

 characteristics required for an ideal numerical model of profile change, but 

 it is recognized that much has yet to be learned about the processes of wave 

 deformation in the surf zone, beach profile change, dune erosion, and 

 overwash. The individual items or requirements listed below are not 

 completely independent of each other but are presented separately for 

 clarity. These 14 items have been placed into four groups: input data and 

 initial and boundary conditions, calculation procedures, model properties, 

 and extendability. Other combinations of properties are possible also. For 

 example, Dally (1980) and Dally and Dean (1984) have presented five criteria 

 which a "good" beach profile model should satisfy. The four criteria for an 



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