PART IV: REPRESENTATIVE CHARACTERISTICS OF THE DATA SET 



39. This chapter notes general trends and representative characteris- 

 tics of the data set on profile change obtained with the LWT. Emphasis is 

 placed on time evolution of selected properties of bars and berms. 



40. First, the procedure used to define morphologic features of bars 

 and berms is described. Secondly, profile types are classified as being 

 either bar or berm, and a criterion for distinguishing these limiting profile 

 shapes is developed in terms of the deepwater wave steepness and a dimension- 

 less sand grain fall velocity parameter. Such a criterion can be used di- 

 rectly as a predictor of beach erosion and accretion. Examples of the time 

 evolution of selected bar and berm features are also given. The chapter con- 

 cludes with a discussion of the net cross-shore sand transport rate along the 

 profile and the associated transport rate distributions. 



41. For the analysis, each profile was expressed in a cubic spline 

 representation, resulting in approximately 75 polynomials per profile. This 

 representation facilitated numerical evaluations and gave a continuous mathe- 

 matical description of the profile. Only those cases involving plane initial 

 beach slopes (all cases except Cases 510 and 610) were used to allow direct 

 interpretation and intercomparison of results. 



42. Numerical values are expressed in metric units. It is emphasized 

 that the original profile survey data listed in Appendix C are given in US 

 customary units, i.e., distances are expressed in feet. 



Definition of Bars and Berms 



43. In a qualitative sense, bars and berms are readily identifiable 

 features associated with local regions of deposition along the beach profile. 

 Figure 5 is a definition sketch for the nomenclature associated with bars and 

 berms that is employed in this chapter. 



44. No commonly accepted procedure exists for defining bars and berms 

 in a quantitative manner. For the purpose of making calculations, bars and 

 berms and their associated properties were defined with respect to the initial 

 profile. This procedure provided an unambiguous interpretation of quantities 

 such as bar/berm volume and height and gave results compatible with the 

 intuitive picture of bars and berms as depositional features. 



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