(g) Investigate the model effects of using monochromatic 

 waves or a wave spectrum to obtain equilibrium beach profiles 

 and longshore transport rates. 



(h) Evaluate the importance of the long-wave components 

 of the spectrum in the transport of bottom sediment. 



(i) Complete a comprehensive three-dimensional, movable- 

 bed scale-model study based on the research areas above. Hope- 

 fully, this will establish the necessary scale-model laws, con- 

 fidence in scale-model results, and procedures for subsequent 

 efforts. 



(j) Conduct a postconstruction verification study of the 

 scale-model results. This requires extensive prototype meas- 

 urements, and perhaps fairly extensive additional scale-model 

 tests. 



7. Summary . 



Movable-bed scale-model investigations of coastal erosion and coastal 

 sediment transport phenomena are probably the most difficult hydraulic 

 models to conduct. However, such model studies are feasible in certain 

 circumstances; careful planning is required, and the acquisition of ex- 

 tensive and accurate prototype data is necessary. Numerous scale-model 

 laws can be derived by making various assumptions regarding the physical 

 processes governing sediment motion. 



The most important phase in this type of scale-model study is to ob- 

 tain the quantity and quality of prototype data required for model ver- 

 ification. Some of the many problems that must be dealt with in model 

 operation are model circulation, type of bottom sediment, model size, 

 and rapid measurements and remolding of bottom topography. Although 

 nearly quantitative movable-bed scale-model investigations of some 

 coastal erosion and coastal sediment transport problems are considered 

 feasible, a considerable amount of additional applied research is neces- 

 sary before such studies become routine. 



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