

1 













- 











.8 



- 











5 



















V \ 1 



z 









s \ 







UJ 









\ \ I 







o 





- 





\ \ 



^ \ ' 







Ll_ 



.6 







\ \ I 







Ld 

 O 









\ \ I 



\ \ I 







o 





- 





\ \ 







-z. 

 o 



.4 







\ \ I 

 \ \ 

 \ \ 







CO 

 CO 







x \ 







2 









I n\ 







CO 















z 















< 









I V. 







cc 















1— 



.2 







\ \ 

 \ \ 

 i \ ^ 

 I \ x 



\ N 



I \ \ 















I 



I I I I I I 



I 















— 



5 



-4 



-3-2-10 1 2 



3 4 5 











RELATIVE CREST HEIGHT Rc/Dn50 







Figure 54. Basic graph for wave transmission versus relative crest height (Van der Meer 

 1991) 



two most important variables that influence wave reflection from a low-crested 

 structure are the relative depth, h/L and the relative height, hjh (Ahrens and 

 Cox 1990). Ahrens (1987) presents a formula for predicting the reflection 

 coefficient for a reef breakwater. 



K r = exp 



u 



p) 



C2 



K 



h 



+ C, 



2 



c 4 



R. \ 



H_ 



(44) 



where 





-6.774 

 -0.293 

 -0.0860 

 +0.0833 



The ACES module "Wave Transmission Through Permeable Structures" 

 also provides a method of determining a reflection coefficient. Other factors 

 being equal, reflection coefficients increase with increasing wavelength and 

 increasingly steeper slopes. Reflection coefficients also increase with 



Chapter 4 Structural Design Guidance 



93 



