indicates that large portions of the surveyed profiles were above water or in 

 the swash zone most of the time. Criteria such as Equation 2 are applicable 

 to the total surf zone profile extending from the berra to the main breakpoint 

 bar and to prediction of major changes in it. In a strict sense, wading depth 

 profiles do not provide a suitable data base for investigating beach erosion 

 and accretion predictions since it is not known if sediment volume is con- 

 served. Wave heights given by Seymour (1985) were shoaled to deep water using 

 linear wave theory to provide a better estimate of the significant deepwater 

 wave height H^^ than the value at the gage. Water temperatures, needed to 

 calculate sand fall speed, were obtained from tables given in a University of 

 California (1982) publication for the California beaches and from data 

 available at the US Army Engineer District Norfolk, for Virginia Beach*. The 

 data of Sunamura (1980) were used directly, with the given wave height 

 interpreted as significant deepwater wave height. 



225. The total field data set was tested using Equation 2, with the 

 deepwater wave height taken as either the root mean square H^.^^ , mean H , 

 or significant wave height Hg^ . These wave heights were calculated using 

 the relationships Hj.^^ = 0.706 H^^ and H = 0.626 ti^^ , derived under the 

 assumption of a narrow banded wave frequency spectrum, for which the wave 

 height follows a Rayleigh distribution (Longuet-Higgins 1952). Plots made 

 using the three statistical wave heights showed that the data separated into 

 two approximately distinct groups, similar to Figure 6 for regular waves. For 

 the wave heights U,.^^ and Hs^ , the values of M in Equation 2 were 

 different from 0.00070 found for regular waves. However, when H was used, 

 Equation 2 with M = 0.00070 was found to separate the eroding and accreting 

 cases reasonably well, as shown in Figure 10. The lines drawn in Figures 6 

 and 10 are identical, indicating that mean wave height is the appropriate 

 statistical wave height to use in comparisons of erosion and accretion 

 occurring in the field with that generated by prototype -scale regular waves. 



226. As previously mentioned, the data of Seymour (1985) were censored 

 to restrict analysis to times of larger rates of change of the profile. In 

 the censored data set, some points remained which appear anomalous if viewed 



Personal Communication, 1988, Paul Bowen, Geologist, US Army Engineer 

 District, Norfolk, VA. 



73 



