wave data) of the computational grid at an incident angle equal to the central 

 angle of the angle band. The model then calculated the wave transformation 

 over the actual bathymetry to the wave break point. The results (wave height 

 transformation coefficient and nearshore incident wave angle) were saved at 

 grid points alongshore at a nominal depth of 15 ft. The results were written 

 to a data base and keyed to the input angle band and wave period. This 

 allowed the shoreline change model to read the offshore wave conditions at a 

 specific time step and calculate a key based on the incident wave angle and 

 wave period. The key was then used to identify the corresponding nearshore 

 wave conditions along the project coast. Using this methodology, nearshore 

 wave heights and incident angles were obtained at 600-ft intervals for input 

 to the shoreline change model. The use of RCPWAVE in this manner allowed the 

 shoreline change model to account for major bathymetric features offshore 

 which may cause convergence of divergence of wave energy along the coast. 



SHORELINE CHANGE MODEL 



The acronym GENESIS stands for GENE ralized model for Simulating Shore- 

 line change. A detailed description of the model is provided in Hanson (1987, 

 1989) and Hanson and Kraus (1989). GENESIS is a generalized system of 

 numerical models and computer subroutines which allow simulation of long-term 

 shoreline change under a wide variety of user-specified conditions. 



GENESIS calculates local wave breaking, longshore sand transport rate, 

 and the resulting plan shape evolution of the modeled coast. The effect of 

 natural features such as sea cliffs, and coastal structures and activities 

 such as seawalls, groins, and beach fills are incorporated in the model by 

 modification of the transport rate through boundary conditions and con- 

 straints. The diffraction effect of detached breakwaters and long groins on 

 the local wave climate is represented around and behind these structures. 

 Kraus (1989) describes the capabilities and limitations of the model. 



GENESIS can be utilized with two types of wave inputs depending on the 

 available data and degree of computational effort required. A single offshore 

 or deepwater wave condition can be input, and the wave model within GENESIS 

 will calculate breaking wave conditions along the modeled reach. Alternative- 

 ly, a more sophisticated wave transformation model which describes wave 

 propagation over the actual offshore bathymetry (such as RCPWAVE) can be used 



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