20 



10- 



Q 

 > 



CD 



c 



.Q -10 



-I—' 



CD 

 > 



LU 



-20 H 



-30 



-Initial 



- Constructed 



- EBP1 

 -EBP2 



-200 



200 400 600 800 1000 1200 1400 



Distance from Baseline (ft) 



Figure 19. Illustration of method determining initial shoreline position 



As^S-Ay 

 where 



(3) 



As = distance from construction template shoreline to corresponding 

 equilibrium beach profile 



S = distance between EBPl and construction template shoreline 



Groin permeability. Structure pemieability in GENESIS defines the degree 

 to which longshore sand transport can pass through or over a littoral barrier. The 

 permeability assigned to a structure is difficult to define based on dimensions and 

 characteristics of the structure and is typically determined during model calibra- 

 tion. Permeability of the structures within the modeling domain of this study was 

 determined during calibration by comparison of modeled groin offsets to those 

 recorded in aerial photography. Typical groin penneability resulting from cali- 

 bration ranged from 0.30 to 0.45. Groin 44 was modeled with zero permeability 

 because its hooked shape and resulting updrift fillet allow little wave action to 

 mobilize sand through the groin. 



Chapter 3 Functional Design 



23 



