which, if shore-parallel transport of that material were highly effective, might 

 lead to a downcurrent buildup. Intermittent coastal currents, e.g., wind-driven 

 currents, were capable of transporting sediment alongshore. An alongshore build- 

 up of disposal material occurred in those profiles directly adjacent to the 

 disposal area. The lateral movement of the more seaward material is interpreted, 

 though, to be primarily a result of storm-generated transport along the bar axis. 

 Also, it is likely that sediment moving alongshore, but seaward of the bar, would 

 not move in the form of a large, discrete bed form, but rather as discrete par- 

 ticles comprising an unnoticeable, sheetlike layer. Nonetheless, the relatively 

 small volume of shore-parallel accretion in the adjacent offshore zone, and the 

 timelag between inshore filling of the surf zone and alongshore buildup in the 

 offshore zone, suggest that shore-parallel transport of disposal sediment was 

 much greater in the surf-dominated inshore zone than in the adjacent seaward off- 

 shore zone. Thi^ is supported by the fact that diver observation and current 

 meter data showed the shore-parallel component of flow for the surf zone to con- 

 sistently exceed that of shore-parallel flow seaward of the surf zone. 



4. Storm Effects . 



Storm-induced currents of the 16 September storm had the effect of trans- 

 porting disposal sediment onshore and alongshore to cause erosion at the up- 

 current end of the disposal bar, and lateral bar growth at its downcurrent end. 

 Some sediment may have been transported offshore, but a more seaward storm bar 

 or a noticeably built-up bottom was not observed. It is likely that most of 

 the sediment filling the northeast (upcurrent) end of the trough came from the 

 adjacent eroded bar in response to wave and longshore transport. Downcurrent, 

 where the disposal trough was not filled, well-developed troughs were cut into 

 the disposal platform or deeper into an already developed disposal trough. 

 However, sediment at these locations also accreted to the inshore margin, per- 

 haps in response to landward sediment transfer across the upcurrent trough and 

 in response to shielding from storm wave erosion by the disposal bar. 



The disposal bar, thus, acted in part as a storm bar during the increased 

 energy conditions. During fairer weather conditions, disposal sediment tended 

 to move landward and ultimately develop a platform. Presumably, depending on 

 breaker type (i.e., plunging versus spilling), breakpoint location, and long- 

 shore current velocity, a trough was maintained. 



Evidence indicates that the overall bulk of net sediment displacement 

 occurred in the inshore and shallowest part of the offshore subzones, particu- 

 larly along the bar and trough complex. This is in accord with the findings of 

 recent transport studies conducted by Kamphuis and Readshaw (J.W. Kamphuis, 

 Queen's Uinversity, Kingston, Ontario, personal communication, 1978). Using a 

 three-dimensional, coastal basin model, they found that for the simulated sum- 

 mer wave cycle (minor storm conditions) onshore transport prevailed until sedi- 

 ment reached the inshore zone. Then, predominant transport became longshore. 

 For a barred profile, in which the bar was a storm bar, most of the sediment 

 transport during fair-weather conditions occurred landward of the bar in the 

 swash and surf zones. During storm conditions in which waves broke upon the 

 seaward bar, the zone of maximum transport was predominantly shore-parallel 

 along the bar crest with essentially no effect on the beach. 



By mid-October, shore-parallel transport from the southwest had been suf- 

 ficient to cause a renewed lateral growth of the bar toward the northeast. In 



37 



