C = 0.51 - 0.11 



(2) 



where B is the structure crest width and h the structure height. Equation 

 (2) is valid for the range < B/h < 3.2. Equation (1) slightly underpredicts 

 the transmission coefficient for submerged breakwaters with a 1 on 15 bottom 

 slope in front of the breakwater; a revised formula is suggested for those 

 cases: 



F 



K. 



■To 



= c(l-f)-(l-2c) 



R 



(3) 



III. ESTIMATION OF WAVE RUNUP 



Values of wave runup on the structure are necessary to use equation (1) . 

 If the runup exceeds the breakwater freeboard, transmission by overtopping will 

 occur. The recommended runup equation for smooth slopes is given by Franzius 

 (1965) / 



where 



R = HC-, 



(0.123 I) 



Wd + C^ j 



(4) 



H or H. 



= incident wave height 



L = wavelength 



d = water depth 



C , C , and C = empirical coefficients. 



Values of the empirical coefficients are given in Table 1. A linear interpo- 

 lation of these values is necessary to obtain coefficients for other slopes. 



Table 1. Empirical wave runup prediction coefficients 

 for smooth impermeable slopes. 



Front- face slope 

 of breakwater 



4 



^2 



^3 



Vertical 



0.958 



0.228 



0.0578 



1 on 0.5 



1.280 



0.390 



-0.091 



1 on 1.0 



1.469 



0.346 



-0.105 



1 on 1.5 



1.991 



0.498 



-0.185 



1 on 2.25 



1.811 



0.469 



-0.080 



1 on 3.0 



1.366 



0.512 



0.040 



The recommended equation for estimating runup on rough slope impermeable 

 breakwaters is given by Ahrens and McCartney (1975) : 



/ aS \ „ ^ tan 6 



(5) 



