A6 



Aerial photography analysis. Seven sets of aerial photographs of the 

 project area shoreline from 1962 to 1985 were analyzed for evidence of 

 longshore sediment transport direction. The results of the aerial photography 

 analysis and field observations supported the results of the analytical 

 determination of the longshore transport in the area. Overall, there appears to 

 be a net longshore transport to the north along the study area shoreline with 

 some occurrence of southerly transport. The best estimate for the magnitude 

 of the net transport rate is approximately 5,000 to 10,000 cu yd/yr to the 

 north. 



Structural Breakwater Design 



Design wave and water level 



The level of structure design was the 25-year storm event. Based on the 

 numerical modeling analysis, the design wave height H s , wave period T, and 

 storm surge DSWL for this event are: 



H a = 6.5 ft 

 T = 7.6 sec 



DSWL = +5.2 ft mlw 



Breakwater stone size and cross section 



Selection of the armor stone size to withstand the design wave conditions 

 was based on the stability formula developed at the U.S. Army Engineer 

 Waterways Experiment Station. This formula is as follows: 



w r H 3 

 W = r . (A2, Equation 7-1 16, SPM) 



K D fS. - l) 3 „ 



where 



W = weight in pounds of an individual armor unit in the primary cover 

 layer. The stones comprising the primary cover layer range from 

 about 0.75 Wto 1.25 W, with about 50 percent of the individual 

 stones weighing more than W 



w T = unit weight of stone; 165 lb/ft 3 



H = design wave height at the structure; 6.5 ft 



S T = specific gravity of the armor unit, relative to the water at the 

 structure (S r = w,/w w ); 2.58 



Appendix A Case Design Example of Detached Breakwater 



