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4 40 3.1 Model Formulation and Model Setup The EFDC code has been widely used to simulated hydrodynamics and water quality in shallow marine environment (Appendix A). The code already includes a number of extensions and improvements for more accurate simulations. Many of these extensions have heen added by Florida Tech (Zarillo; 1998, Zarillo and Yuk. 1996) includine a • 1 number of subroutines for simulation of nearshore wave -induced currents and noncohesive sediment transport. Relevant extensions include: a wave -current boundary layer formulation similar to that of Grant and Madsen (1986); modifications of the hydrodynamic model's momentum equations to represent wave period averaged Eulerian mean quantities; the inclusion of the three-dimensional wave -induced radiation stresses or Reynolds stresses in the momentum equations; and modifications of the velocity fields in the transport equations to include advective transport by the wave induced Stoke's drift. In the original application of EFDC to Vero Beach, the REF/DIF wave model (Kirby and Dalyrmple, 1994) provided a steady-state surface wave field. Reynolds Stresses from the wave field was then read into EFDC to provide wave forcing in the momentum equation. In the new application of EFDC to Vero Beach, an internal mild slope wave equation submodel similar to that of Madsen and Larsen (1987) will be executed within the EFDC modeling scheme. This will be accomplished on a fine -scale subgrid of high enough resolution to accommodate surface gravity waves. Thus, EFDC will alternate between calculation of circulation and sediment transport on the main computation grid and frequent updates of the wave field on the sub -grid. An additional extension of the EFDC model version for this project (EFDC2) will be a sediment mass conservation submodel that will simulate changes in bed elevation (topography) as a result of predicted sediment transport. The basis for these extensions has already been accomplished to a limited degree in the first phase of the PEP Reef project completed in 1996. However, additional work is required to use the model in a time -marching mode that will realistically simulate hydrodynamics and topographic