a beach fill added between the measured post-fill shoreline on July 8, 1991 

 and the measured shoreline on September 28, 1991. The added berm width, 

 YADD, was selected to be 10 ft, which was the average bayward 

 displacement of the shoreline opposite the breakwater gaps between the two 

 measured shorelines. The volume of the "artificial" beach fill approximated 

 the volume of eroded material in the berm scarp. 



Results of this simulation are shown in Figure A14. In general, the 

 agreement between the measured and calculated shoreline is greatly improved 

 with a CVE equal to 7.89. 



At this point, the model was considered to be calibrated sufficiently and the 

 verification process was initiated. The intent of this process was to use the 

 model to reproduce a measured shoreline over a time interval independent of 

 the calibration interval. The shoreline selected for verification of the model 

 was the measured shoreline of November 17, 1991, since hindcast wave data 

 were also available through that period. The model parameters used for the 

 verification simulation were the same as for the last calibration simulation. 

 Results of this simulation, shown in Figure A15, indicate good agreement 

 between the measured and calculated shoreline positions, with a CVE equal to 

 7.51. 



Summary and Discussion 



The preceding sections discuss the data preparation, calibration, and 

 verification of the GENESIS model for the Bay Ridge offshore breakwater 

 project. A detailed description of many of the intermediate simulations is 

 omitted. 



Overall, the agreement between the measured and calculated shorelines 

 during the calibration and verification stages is considered to be good 

 considering the limitations of some of the data used. In particular, the 

 wave data set was developed using wind data from an inland anemometer 

 nearly 20 miles away from the site and hindcast techniques using the shallow- 

 water wave equations. The use of actual wave data from the site or a more 

 sophisticated wave hindcast would have more than likely resulted in better 

 agreement between the measured and calculated shoreline positions. In 

 addition, the scarping and erosion of the storm berm after initial placement, 

 which resulted in a bayward advancement of the shoreline opposite the 

 breakwater gaps, further complicated the modeling effort. 



In any event, the agreement obtained between the measured and calculated 

 shoreline positions even with the data limitations, clearly illustrates the 

 capability and effectiveness of the GENESIS modeling system in simulating 

 the influence of waves and coastal structures on the evolution of a sandy 

 beach. The results demonstrate that the modeling system is an extremely 

 useful engineering tool for evaluating shore protection projects. 



Appendix A Case Design Example of Detached Breakwater 



A25 



