to within ±25 percent for base and Plan 1 conditions. 



129. To keep things in perspective, it should be pointed out that at 

 present the only possible alternative to a numerical sediment transport model 

 is a physical movable-bed hydraulic model. Movable-bed coastal models are 

 fairly complicated and expensive to construct and operate. Such models 

 require more time than a numerical modeling effort. At present, there is no 

 universal agreement on the scaling relations to be used. Movable-bed coastal 

 models involving the combined action of waves and currents near inlets (the 

 type required by the present study) are the most complicated of all coastal 

 models and the least understood. Their results are approximate because there 

 has to be a compromise between scaling relations necessary for waves only and 

 scaling relations required for currents only. According to established ex- 

 perts, the accuracy of a coastal movable bed model of this type in the hands 

 of an expert will be of the order of ±50-100 percent. Thus, the results of 

 the numerical modeling system employed in this study are definitely better 

 than the alternative. 



76 



