line) after approximately 80, 370, and 1,650 waves. Figure E20 in Appendix E contains the complete set of 

 comparisons. Wave analyses, profile soundings, and profile plots for test Til are given in Appendices B, C, 

 and D, respectively. 



218. The comparisons in Figure 32 were quite similar to the regular wave comparisons of T03 and TIO. 

 Initially, the profile development is very similar with little diiTerence apparent between the two tests. 

 Eventually, as the tests approached equilibrium, the seawall began to affect profile evolution with increased 

 erosion in the surf zone region and removal of sediment across the crest and seaward slope of the slight bar 

 feature as shown after 1,650 waves. Interestingly, there is a fairly uniform distribution of the additional 

 erosion due to the vertical seawall, and the variety of waves in the irregular wave field helped to smooth the 

 profile response. As in the regular wave case, no systematic differences in wave statistics or reflection 

 coefficients were evident, and profile evolution also appeared to progress at similar rates. 



219. As is typical in laboratory tests involving irregular waves, cross-tank variation in the profile was 

 visually observed to be minor, although no sidewall profiles were obtained to document this observation for 

 test Til. The additional eroded area on the center-line profile seaward of the seawall was calculated to be 

 1.49 ft^/ft compared with the measured withheld sediment quantity of 1.79 ft^/ft- Hence, the eroded 

 volume for this case was about 83 percent of the withheld volume, a smaller percent than was obtained 

 with regular waves, but still considerably higher than the average of 61 percent reported by Barnett (1987). 



Regular Versus Irregular Wave Effects 



220. Test Til with the vertical seawall in place represented the irregular wave counterpart of test TIO 

 with i/1/3 of the irregular wave train being nearly equal to the monochromatic wave height and the peak 

 spectral period of the irregular waves equal to the period of the regular waves. Profile evolution for these 

 two cases is compared in Figure 33 at 80, 370, and 1,650 waves. The complete set of comparisons is in 

 Figure E21 in Appendix E. 



221. Generally, the comparison is satisfactory throughout the profile development with the irregular 

 wave condition (solid line) producing about 0.53 ft^/ft less surf zone erosion after 1,650 waves and 

 exhibiting a smoother shape, as was expected. This result agrees with earlier comparisons between regular 

 and irregular waves presented in Part VI and further supports the conclusion that the irregular wave 

 parameter /fi/3 best represents the monochromatic wave height in the situation of profile development. 



222. After the initial adjustment in the early stages of the experiment, time for profile evolution in the 

 irregular case appeared to lag the regular wave profile development by a factor of approximately two. 

 Figure 34 compares time-shifted profiles where the time for development in the irregular wave case is about 

 twice as long as in the regular wave case. All time-shifted comparisons exhibit better correspondence than 



