2. Beach Profile Parameters . 



The terminology for the coastal zone used in this report is described 

 in Figure 1. Noda's (1972) law was based on modeling the "equilibrium 

 profile" and, although there is a wealth of published profile data, 

 most of the data are not useful because the profiles were formed under 

 many varying wave conditions or, in laboratory experiments, under differ- 

 ent experimental procedures. The figure illustrates the two most broad 

 classifications of beach profiles as a bar-type or step-type. 



Equilibrium profile implies a profile whose mean position is fixed 

 in space for the given wave conditions, with the expectation that the 

 actual profile at any given time will deviate from the mean profile; 

 also, equilibrium is a state which will be reached on a model beach 

 subjected to constant wave action for a sufficiently long time. The 

 equilibrium profile of a beach is a function of the wave characteristics 

 such as wave height, wavelength, wave period, and the sediment charac- 

 teristics (e.g., specific gravity and median diameter). 



A noticeable distinction of both laboratory and prototype beach 

 profiles is the formation of "winter" (bar) and "summer" (step) shapes 

 under different deepwater wave-steepness conditions (Hq/Lq) • The winter 

 or "storm" profiles (Fig. lb) are usually formed under large wave-steepness 

 conditions and are characterized by the erosion of material from the fore- 

 shore zone to the offshore zone, producing a flatter foreshore gradient 

 and the distinctive formation of longshore bars. The summer or "ordinary" 

 profiles (Fig. la) are usually produced under small wave-steepness condi- 

 tions and are characterized by an accretion of material on the beach face 

 and in the breaker zone, producing a steep foreshore slope and no longshore 

 bar formation. This is an oversimplification because it is possible to 

 have beach profiles between these two idealized types, and other compli- 

 cations, including multiple bars, are frequently found. On prototype 

 beaches the actual beach profiles are functions not only of the waves and 

 sediment present, but are greatly influenced by the availability of lit- 

 toral supply of sediment. 



Johnson (1949) suggested the range of deepwater wave steepness 0.025 

 to 0.03 alone represented the transition zone between summer and winter 

 profiles. Watts (1954) and Rector (1954) indicated that although the 

 deepwater wave steepness was important, other parameters such as sand 

 characteristics affected the beach profile. Saville (1957), testing 

 under prototype conditions, found that for a wave steepness as small as 

 0.0023, a winter- type beach was formed. 



Bagnold (1940) suggested that the ratio of the deepwater wave height 

 to the grain diameter was an important parameter in obtaining beach profile 

 similarity. Bascom (1951) added credibility to this parameter by showing 

 that for prototype conditions the foreshore slope was related to the 

 median-grain diameter. Wiegel (1964) extended this data and showed the 

 effects of changes in the wave characteristics. 



