150,000 cu yd/year of sediment across the entrance system both from the north- 

 west to the southeast and vice versa. 



The results of the baseline sand management simulation plan "A" (Alter- 

 native 8, simulation code SM2A) are plotted in Figure 11. The impacts of he 

 entrance system with sand management plan "A" in place are shown in Figure 12. 

 As depicted in Figure 12 adverse impacts on adjacent shorelines attributable 

 to the entrance system are mitigated to the prescribed level stated above. 



SUMMARY AND CONCLUSIONS 



The shoreline change model GENESIS was utilized in conjunction with 

 other numerical models to quantify potential shoreline impacts of constructing 

 a structured inlet entrance system at Bolsa Chica, California. The shoreline 

 modeling task provided estimates of gross and net longshore sand transport 

 rates along the project reach, and allowed investigation of the technical 

 feasibility of mitigating potentially adverse shoreline impacts resulting from 

 the proposed entrance system. 



This study of the longshore sand transport processes and shoreline 

 response resulting from the construction of the proposed ocean entrance system 

 at Bolsa Chica Bay has shown that mitigation of any adverse impacts on the 

 adjacent shorelines is feasible. Based on the results of the model simula- 

 tions presented above the following conclusions are made: 



a. The proposed site of the new entrance system is located 

 in a region of converging longshore sand transport, i.e., 

 sand is transported toward the entrance system from both 

 upcoast and downcoast. 



b. Locating the entrance system approximately 1-mile 

 upcoast or downcoast from the proposed site will not sig- 

 nificantly change the estimated shoreline response. 



c. Implementation of a sand management plan and infrastruc- 

 ture capable of the minimum requirements stated above will 

 allow for the mitigation of adverse shoreline impacts. 



d. The Surfside- Sunset feeder beach nourishment program 

 must be continued in order to maintain the shoreline within 

 2 miles of the Anaheim Bay entrance. However, the proposed 

 entrance system at Bolsa Chica will neither aggravate nor 

 improve the situation. 



84 



