ARMOR STONE ■— ^ 



1.5 yf 



BEDDING STONE -^ yS \ 



1 5 ' 





1.5 



I 





V^N/ — \ 



\^ . 3 ' 





\ P 



-1.5 ^xjoc{Jrxi\ 



T MINIMUM 





ELK NECK 



Figure 56. Cross section of reef breakwater at Redington Shores at Pinnelas County, 

 Florida (Ahrens and Cox 1 990) 



I 12 ' 



1.5 



.i 1 n/ 



3 STONES (12") 



-9.5 



I" "I EL 1.5 



/ \ 1.5 



wi \rii ?■ 



EL -4.5 1.5 | 



— 1 X 



\ I" '1 EL -6.5 

 ^ — EXISTING BOTTOM \ V \. 



^ — 7^\V W3<-^\ ! " 5 



^W2^--X > X~I1 EL 



-/— ^W3^— 



EL -9.5 / / 



~/^H2r~~~ 







> * FILTER CLOTH 



REDINGTON SHORES 



Figure 57. Cross section of reef breakwater at Elk Neck State Park, Maryland (Ahrens and 

 Cox 1990) 



Jetties. The design and construction of low-crested breakwaters, including 

 reef breakwaters, uses similar procedures to those specified in the above 

 manuals, but involves different design guidance for several steps in the 

 procedure. 



Crest height, crest width, and structure slope 



Iterative analyses involving the assessment of a range of crest elevations, 

 crest widths, and structure slopes are required to determine the influence of 

 each on both stability and functional performance and ultimately develop the 

 optimum cross section. The crest elevation of a low-crested breakwater is one 

 of the most critical parameters in the cross sectional design due to the 

 considerable influence of crest elevation on both structural stability and 

 functional performance. Small changes in crest elevation can result in 

 significant changes in stability and wave transmission characteristics. The 

 crest width and structure slope also influence stability and performance of the 

 structure; however, less dramatically than crest elevation. Therefore, these 

 parameters often follow guidance and ranges used for conventional structures. 



96 



Chapter 4 Structural Design Guidance 



