zone and a subaerial zone. The two zones shift with changes in water level. 



12. The subaqueous portion of the beach profile is in continuous 

 motion under hydraulic and mechanical forces produced by waves and currents. 

 The regions of most intense sediment movement are located in the surf zone, 

 from the location of wave breaking to the point of maximum wave uprush. 

 On-offshore sediment transport is particularly intense in the swash zone and 

 in the area of the break point of the incident waves. However, sand is in 

 continual motion all along the subaqueous profile. 



13. The subaerial portion of the beach also changes. Berms build 

 during calmer wave conditions. Sand from the berm may be blown onshore to 

 form dunes, or they may be created artificially. If the water level rises, 

 the formerly subaerial portion of the beach will be unstable relative to 

 sediment moving hydraulic forces. The berm and dune can erode by overwash 

 (transporting sand landward) or by scour and collapse (moving beach and dune 

 sediments seaward). 



14. Beach profiles are typically classified into two basic types, 

 either depositional (also normal, summer, swell, step type, or reflective) or 

 erosional (also storm, winter, bar type, or dissipative) as shown in Figure 

 3. Other, more detailed classifications have been proposed (Sunamura and 

 Horikawa 1975, Wright et al. 1979, Hattori and Kawamata 1981, and Wright and 

 Short 1983). 



Factors Contributing to Profile Change 



15. Bruun (1962), Edelman (1968, 1972), Dean (1977), Vellinga (1983b) 

 and others have identified an increase in water level as the most important 

 variable relating to dune and shoreline retreat. During a storm, the "storm 

 surge" develops as a result of the superposition of the astronomical tide, 

 wave setup, and meteorological (wind and pressure induced) surge. This 

 abnormally high water level permits erosive waves to attack the subaerial 

 beach. On a less energetic scale, it has been well documented (Inman and 

 Filloux I960, Otvos 1965, and Hattori 1983) that cross-shore movement of 

 sediment is closely related to the tide level. 



16. A change in water level does not cause erosion; wave action is 

 required to move the sediment. It was recognized early in the study of 

 coastal processes (Johnson 1952) that deepwater wave height and wave 



