8. CONCLUSIONS AND RECOMMENDATIONS 



The framework of a comprehensive model for coastal currents and sediment 

 dispersion is formulated. Results of the present study and future studies 

 needed are surmiarized in the following for various components of the overall 

 model . 



An efficient three-dimensional and comprehensive numerical model of 

 coastal currents has been developed and is operational. It may be used to 

 provide detailed computations of the currents within several tidal cycles or 

 time scales of a storm event. With some modification, it could be combined 

 with a vertically-integrated model for long-term computations on the order of 

 weeks, months, or longer. 



Applications to the Mississippi Sound and adjacent offshore waters showed 

 that large spatial and temporal variation of currents and bottom shear 

 stresses exist within the area. Model simulations during 9/20/80 to 9/25/80 

 and 6/12/80 to 6/16/80 agree very well with measured data on surface 

 displacements and currents. 



To better understand the effect of open Gulf circulation on the currents 

 in the study area, the present three-dimensional model may be modified to 

 compute the entire Gulf circulation on a relatively coarse grid. The results 

 will then provide boundary conditions for the finer-grid, limited-area model 

 used in the present study. Further studies on density-driven currents should 

 also be planned with comprehensive measurement programs. 



The role of turbulence in affecting the deposition, entrainment and 

 transport of cohesive sediments has been large oversimplified in the past. We 

 have provided a thorough review and quantitative analysis on these aspects. 

 For example, for cohesive sediments in a coastal environment, our analysis 

 indicates that sediment particle dynamics is important and can be modeled by 

 considering a number of particle groups and the coagulation process. 

 Theoretical study on deposition of cohesive sediment is lacking and is needed. 



Detailed dynamics within a turbulent boundary layer, under pure wave or 

 wave-current interaction, has been studied by means of a turbulent transport 

 model. Model predictions compare well with data and are more accurate than 



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