applying a similar approach in analysis of field data where profile change is 

 produced by the combination of a number of different forcing agents and is 

 prone to ambiguity. 



Data Analysis Procedure 



186. In this study, morphologic profile features of interest are forma- 

 tions created by wave action, directly or indirectly, during time scales much 

 greater than the wave period. To numerically evaluate properties of morph- 

 ologic features , the survey data were approximated by a set of cubic spline 

 polynomials, producing on the order of 75-250 polynomials per profile. This 

 representation allowed geometric properties such as volumes, distances, 

 depths, and slopes to be determined analytically once the spline coefficients 

 were calculated. Also, by using the interpolation polynomials, a continuous 

 and accurate description of the profile depth with distance offshore was 

 obtained from the discrete depth values at survey points. 



187. A fundamental problem immediately encountered in quantitative 

 analysis of a morphologic feature is specification of an unambiguous defini- 

 tion that will preserve the characteristics intuitively associated with it. 

 For example, a bar is normally considered to be a subaqueous accretionary 

 feature formed of sand redistributed and deposited along the profile. From 

 observation of a natural barred beach profile it is easy to determine the 

 crest of a bar and hence the approximate location of the bar, whereas it is 

 much more difficult to define or agree upon the exact cross -shore length of a 

 bar, a quantity which is needed if a volume calculation is to be done. 

 Keulegan (1945) used the concept of a barless beach profile to which bar 

 properties could be referenced. The barless profile is constructed by drawing 

 lines joining maximum trough depths along the profile with the point of zero 

 depth. Apart from the arbitrary nature of this definition, it is sometimes 

 difficult to determine the seaward limit of the bar by this method. 



188. Use of points where the second derivative (radius of curvature) is 

 zero to define a bar is found to be convenient if applied on the shoreward 

 side of a bar, where the curvature of the profile changes sign going from 



56 



