In contrast to the summer study period when beach morphology was 

 characterized by large ridge and runnel systems, welded ridges, and wide 

 low tide terraces, beach morphology for the winter study period consisted 

 of typical early preweld and late preweld profiles characterized by neap 

 berms, beach cusps, and small ridge and runnel systems. Poststorm pro- 

 files at PL-0, PL-5, PL-6, and PL-11 are shown in Figures 62 and 63. A 

 similar situation on profile PL-0 existed during the summer period. 

 Profile PL-0 responded more quickly after the storm than other profiles 

 characteristic of the central and northern parts of the study area. The 

 incipient berm was not removed on PL-0 during the storm of 7 January as 

 on the other profiles. Profiles PL-6 and PL-11 (Fig. 62) representing 

 the central and northern parts of the area do not exhibit different 

 stages of beach maturity as exist between PL-0 and PL-5. 



Continued neap berm accretion between 10 and 17 January resulted in 

 the profile changes on PL-6 (Fig. 64). The change in slope of the beach 

 face was due to the highest breaker-power measurements of the study 

 period on 17 January before the measurement of the beach profiles. Pro- 

 file PL-11 on 10 and 17 January was run through a bay between beach cusps, 

 explaining why a well-developed neap berm was not present. 



Beach cusps which commonly develop during the initial stages of early 

 accretionary beach morphology were ubiquitous throughout the study period. 

 The spacing of the cusps varied between 25 and 30 meters (Figs. 65 and 

 66). 



Detailed mapping of the cusps between PL-0 and PL-4 did not reveal 

 any significant migration under varying energy conditions. Beach cusps 

 have been observed to have a controlling influence on the direction and 

 intensity of longshore drift under certain conditions. Field observa- 

 tions in January 1972 show that at or near high tide, rip currents, 

 caused by the beach cusps, tend to keep beach face velocities within a 

 certain range, regardless of the angle of wave approach. Lower veloci- 

 ties of rip currents associated with low breaker angles (5° to 10°) are 

 "accelerated" as they enter the rip system, and higher velocities asso- 

 ciated with greater breaker angles are "decelerated" as they enter the 

 system, i.e., the velocities within the rip system appear to be rela- 

 tively constant unless the breaker angle or wave conditions are such 

 that a cusp and its associated rip system are completely bypassed. 



The first stages of an early accretional beach profile were present 

 at the conclusion of the study period--a wide low tide terrace, a rela- 

 tively steep neap berm, and numerous beach cusps. Figure 67 shows the 

 similar stages of beach profile development at PL-7 and PL-11 near the 

 termination of the study. The neap berm grew seaward from 25 January 

 until the end of the study because of a marked decrease in breaker 

 power during this time period. 



78 



