breaking properties for the same wave steepness. Reasons the subtest were 

 indeterminate are : 



a. Deviations of the phenomenon were within the range of devia- 

 tion for the experiment. 



b. The range of the variables that determined deepwater wave 

 steepness, H and L , was only a factor of two. 



c. The independent variables, such as f} x and H /L , changed 

 slightly between the base case and variation cases because of 

 limitations in equipment. 



d. Accuracy of the data decreased as the wave height decreased 

 because of limitations in measurements. 



A complicating factor is the wide variability in reflection, which is not 



known. The validity of steepness scaling should be pursued in future work, 



and it is recommended that the various wave conditions be generated on a plane 



slope prior to installing bars to establish a control condition by eliminating 



bar variables that are difficult to specify with precision. 



Irregular Waves 



158. Irregular waves were generated, recorded, and analyzed for 500 

 waves, contrary to the monochromatic wave tests that were analyzed for 15 

 waves. Because wave height and period varied, a longer record was required 

 for the irregular wave tests to obtain a statistically strong confidence 

 interval for calculating the wave spectrum. Reflection and re -reflection 

 between the beach and the wave board could not be avoided in the irregular 

 wave tests. 



159. Maximum, significant, and rms wave height were calculated from the 

 time series of the irregular wave trains and are plotted versus distance from 

 the still-water shoreline in Figures 65(a-c) -68(a-c) . Figures 65(a-c) -68(a-c) 

 show that the difference between H,,,^ , H s , and H^ decreases as the 

 waves enter shallow water, which indicates the distribution of wave heights 

 becomes narrower, i.e., the waves become more "regular." This behavior was 

 also shown in other irregular wave laboratory and field studies , such as 

 Thompson and Vincent (1984) and Ebersole and Hughes (1987). 



160. Wave height decay for the plane-beach tests is extremely gentle, 

 making it difficult to define a mean breaker line as discussed by Thornton, 

 Wu, and Guza (1985). The barred tests depict a decrease in wave height immed- 

 iately shoreward of the bar, but the wave height over the bar (Gage 4) was not 



120 



