h. Perdid o Pass, Alabama . This weir-jetty project was completed in 1969 

 (see Fig. 6-51). Since the direction of the longshore transport is westward, 

 the east jetty included a weir section 300 meters (984 feet) long at an ele- 

 vation of 15 centimeters (6 inches) above MLW. The diurnal tidal range is 

 about 0.4 meter (1.2 feet). A deposif'nn basin was dredged adjacent to the 

 weir and the 3.7-meter-deep channel. The scour that occurred along the basin 

 side of the concrete sheet-pile weir was corrected by placing a rock toe on 

 the weir. Nearly all the littoral drift that crosses the weir fills the 

 deposition basin so rapidly that it shoals on the channel. The first 

 redredging of the basin occurred in 1971. During the period from 1972 to 

 1974, two dredging operations in the basin and the navigation channel produced 

 a total of 596,000 cubic meters (780,000 cubic yards) of sand. Three dredging 

 operations between 1975 and 1979 removed a total of 334,400 cubic meters 

 (437,400 cubic yards) of sand from the channel. In 1980, 175,400 cubic meters 

 (229,400 cubic yards) was dredged from the channel and deposition basin. 

 These figures indicate that approximately 138,000 cubic meters (181,000 cubic 

 yards) of sand is being bypassed each year. 



In 1979 Hurricane Frederic dislodged three sections of the concrete sheet 

 piling in the weir and cut a channel between the weir and the beach. The 

 discharge from the dredging operations that year was used to close the breach 

 and to fill the beach to the east of the weir. 



3 . Addi t ional Bypassing Schemes . 



Several other methods of bypassing sand at littoral barriers have been 

 tested. Land-based vehicles were used in a sand-bypassing operation at Shark 

 River Inlet, New Jersey (Angas, 1960). The project consisted of removing 

 190,000 cubic meters (250,000 cubic yards) of sand from an area 70 meters (225 

 feet) south of the south jetty and placing this material along 760 meters 

 (2,500 feet) of the beach on the north side of the inlet. On the south side 

 of the inlet a trestle was built in the borrow area to a point beyond the low- 

 water line allowing trucks access from the highway to a crane with a 2-meter 

 (2.5-yard) bucket. Three shorter trestles were built north of the inlet where 

 the sand was dumped on the beach, allowing wave action to distribute it to the 

 downdrift beaches. This method is limited by the fuel expense and by the 

 requirement for an easy access across the inlet and to the loading and 

 unloading areas. 



Split-hull barges and hopper dredges can be used to bypass dredged mate- 

 rial by placing the spoil just offshore of the downdrift beaches. A test of 

 this method was conducted at New River Inlet, North Carolina, during the 

 summer of 1976 (Schwartz and Musialowski, 1980). A split-hull barge placed 

 27,000 cubic meters (35,000 cubic yards) of relatively coarse sediment along a 

 215-meter (705-foot) reach of beach between the 2- and 4-meter-depth (7- and 

 13- foot) contours. This material formed into bars that reduced in size as 

 they moved shoreward. This final survey, 13 weeks later, indicated a slight 

 accretion at the base of the foreshore and an increased width of the surf 

 zone. The split-hull barge method was also used with commercially available 

 equipment to place 230,000 cubic meters (300,000 cubic yards) at St. Augustine 

 Beach, Florida, in 1979. 



While this method provides some nourishment and protection to the beach, 

 it is not known how it compares with conventional placement of sand on the 



6-75 



