of major bar or berm development by infragravity waves was found in the 

 literature review. 



235. The type of bars empirically investigated in this study are those 

 formed by waves breaking on beaches exposed to moderate or high wave energy 

 conditions with a moderate tidal variation (For a bar classification, see 

 Greenwood and Davidson-Arnott 1979.) Waves approaching shore on a sloping 

 beach increase in height due to shoaling until depth-limited breaking occurs. 

 The condition for incipient breaking is a function of the local beach slope 

 and the wave steepness (e.g., Weggel 1972, Singamsetti and Wind 1980). As 

 breaking occurs, energy dissipation in the waves increases sharply, producing 

 the necessary work to intensively entrain and transport sediment in the surf 

 zone. The maximum in the cross -shore transport rate appears to be located in 

 the vicinity of the plunge point where maximum energy dissipation occurs. 

 Seaward of the point of maximum energy dissipation, the transport rate 

 decreases, leading to deposition of sediment in this region and bar formation. 

 As the bar grows , the waves break farther offshore and the break point and 

 plunge point translate seaward, causing the location of the maximum transport 

 rate and the bar to move offshore. Material needed to supply the bar is 

 mainly taken from the region of the inner surf zone, resulting in erosion of 

 the subaerial beach. This process continues until a stable beach profile is 

 achieved which dissipates wave energy without significant changes in shape. 



236. A broken wave may, after further travel, reach a stable wave 

 height and reform, depending on the shape of the profile. Dissipation of 

 energy decreases in the reformed waves , implying a corresponding decrease in 

 the transport rate. Eventually, the reformed waves may shoal and break again 

 closer to shore, resulting in a second but smaller bar in the same manner in 

 which the more seaward main breakpoint bar was formed. The described mecha- 

 nism is valid for both plunging and spilling breakers, both producing a trough 

 in the profile shoreward of the break point (Sunamura in press), although the 

 time scale of bar development will be longer under spilling breakers (Sunamura 

 and Maruyama 1987). Figure 13 displays consecutive profiles in time for one 

 of the CE cases (Case 500), showing a typical example of beach profile 

 evolution with a main breakpoint bar and another smaller bar farther inshore. 



79 



