The negative value obtained here is due to the sign convention used by Song 

 and Schiller and actually indicates 5.5 ft of scoured sediment. 



40. In a study performed at CERC during 1991 and 1992, scaled physical 

 model tests were conducted by Fowler (1992) to investigate toe scour in front 

 of a vertical wall. Twenty- two tests were run for various wave conditions and 

 different wall locations relative to the intersection of msl and the pre -scour 

 beach profile. A statistical analysis of the irregular wave results obtained 

 from this study indicates that ultimate scour depth is most correlated to 

 incident deepwater significant wave height, deepwater wave length, and pre- 

 scour water depth at the wall d„. Since only one grain size and one initial 

 beach slope were used in the tests, no conclusions were drawn regarding 

 effects of grain size (fall speed) or initial beach slope. However, it can be 

 argued that for the case of a vertical wall with nearly perfect reflection 

 characteristics, the effects of beach slope and reflections are accounted for 

 by the presence of h„, H OJ and L in the equation. Subject to the constraints 

 shown below, the following equation for prediction of maximum depth of scour 

 is proposed based on a mathematical analysis of the irregular wave data: 



Hj, 



J22.12 hJL +.25 



(54) 



Use of Equation 54 is limited to cases where -0.011 < h^/L^ < 0.045 and 

 0.015 < Ho/L < 0.040. The last condition restricts the equation to use with 

 waves which are typical of most storms. Maximum scour depths predicted by 

 this equation are plotted versus the measured values from the irregular wave 

 tests in Figure 15. 



Smax/Ho Measured Versus Smax/Ho Predicted 



Pooled Data (Fowler, Barnaft, Chesnutt) * 



0.8 

 ?0.7 

 1 0.6 



f 0.5 



?0.4 " 

 I 0.3 



0.2 ■ 



0.1 



■ 



' ' •y' 



S max /H • (22.72 bJL ♦ 03S>> \S 



. Measured = Predicted — , s m 





' Limited to cases where 



// 



-0.011 ■ tVU. < 0015 L 0.015 . H./L, < 0.04 







Smax/Ho Predicted 



Figure 15. Predicted scour depths versus measured scour depths 

 using proposed equation with irregular wave data only 



41 



