From Figure 6, 



Goda^ _ 2 x 1Q -3 (12) 



>TO 



Therefore, 



Q Goda = (2 x 10 " 3 )J( 2 )(32.2)(5) 3 = 0.18 ft 3 /sec/ft of seawall (13) 



Discussion 



26. The data from which Goda derived his monochromatic-wave overtopping 

 curves show much scatter around the curves. Goda says this scatter is caused 

 by the effect of parameters he ignored (including wave period and beach 

 slope). He believes that for a deepwater-wave steepness less than 0.01, the 

 effect of wave period is not significant. In other words, Goda assumes the 

 difference between overtopping caused by monochromatic waves and overtopping 

 caused by irregular seas is mostly due to wave height variation in the 

 irregular seas. 



Battjes' Method 



Description 



27. The SPM method relates waves to runup and then runup to over- 

 topping. A more direct approach is to relate wave characteristics directly to 

 overtopping, as Goda does for vertical seawalls. Battjes (1974) does this for 

 smooth, sloped structures. After deriving an expression for overtopping 

 caused by monochromatic waves, he accounts for the irregularity of seas by 

 assuming that deepwater wave height and wavelength are jointly Rayleigh 

 distributed. 



28. In deriving his monochromatic-overtopping equation, Battjes com- 

 bines a monochromatic runup formula with laboratory results and then fits the 

 equation to Saville's overtopping data to get 



2 

 b = 0.l(l - |) (14) 



where 



R 



b = 



HL >Jtan 9 

 o ' 



b = Battjes' dimensionless overtopping for monochromatic waves 



16 



