16 days after disposal, and 75 percent removed 34 days after disposal ceased. 

 This is an average loss rate of approximately 340 cubic meters per day from the 

 offshore zone. As previously stated, evidence indicates that most of the volume 

 lost from the offshore zone had moved shoreward. The beach zone, including the 

 accreted ridge material, showed a 10-percent gain 6 days after disposal ceased 

 but had decreased by 2 percent 34 days later for a final 8-percent net gain. 

 The inshore zone initially showed a 1.5-percent gain, 6 days after disposal, 

 followed by a slight volume decrease. Thus, net accretion on the beach slightly 

 exceeded that in the inshore zone. The sum of net accretion for both zones does 

 not balance the amount of offshore loss, indicating a loss from the system. 



Movement from the disposal reach was highest in the longshore direction out 

 of the inshore zone. Tracer data from a California study of the nearshore zone 

 show that longshore transport rates are highest for what would correspond to the 

 inshore zone of this study area, next highest for the beach zone, and lowest for 

 the offshore zone (Duane, 1970) . Thus, although the total amount of inshore 

 accretion in this study was low, transport through that zone was probably high. 



Profile data show that although there was little overall change in the shape 

 or volume of the foreshore, accretion did occur farther landward on the back- 

 shore and seaward in the inshore trough. Some of the beach accretion was due 

 to a natural cycle of beach-ridge formation. Once sediment moves landward beyond 

 the foreshore, the probability of entrainment and removal from the backshore is 

 much reduced. A longer residence time is thus expected for particles moved onto 

 the beach than for those moved into the inshore zone. This explains the greater 

 net volume gain for the beach versus the inshore in the study area, even though 

 it is known that a much greater volume of disposal sediment entered and moved 

 through the inshore zone. 



VI. CONCLUSIONS 



The results of this experiment are encouraging with respect to the concept 

 of sand bypassing and beach nourishment using a split-hull type barge. Dredged 

 sediment, similar in grain size to that of the native beach, was placed in a 

 zone between the original 2- and 4-meter depth contours and was moved, by waves, 

 landward into the innermost part of the littoral zone. However, a relatively 

 small part of the total amount placed offshore was accounted for in the surveyed 

 beach and inshore zones. The longshore current was of major importance in moving 

 the disposal material once it reached the surf zone. Instead of moving directly 

 shoreward onto the beach, much of the sand was deflected and eventually moved 

 in a longshore direction, feeding the adjacent littoral zone and beach areas. 



Disposal piles were modified soon after placement to form a bar which even- 

 tually migrated landward. The bar relief and the volume of sediment contained 

 in the bar decreased during its landward migration. By the time the bar reached 

 the surf zone its shape was lost or greatly diminished. 



At the same time the disposal bar was built and began to migrate onshore, 

 the natural surf zone bar, located landward of the disposal area, began to erode 

 and also move landward. Eventually, the surf zone bar was eliminated and its 

 associated trough filled. This trough filling does not just reflect bar dis- 

 placement. Sediment from the offshore also moved landward into the inshore zone 

 and then longshore. This pattern is supported by the combined set of volume and 

 textural data as well as what appeared to be simple filling of the trough away 

 from the immediate disposal area. 



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