has taken place in the sand trap area (see Fig. 6-44). Between 1966 and 1977 



the sand trap was dredged six times for a total of 488,500 cubic meters 



(639,000 cubic yards), which results in an annual average of about 44,400 

 cubic meters (58,000 cubic yards) of bypassed sand. 



d. Sebastian Inlet ^ Florida (Jones and Mehta, 1977). Sebastian Inlet, 

 72 kilometers (45 miles) south of Cape Canaveral, is a manmade inlet that was 

 opened in 1948 and subsequently stabilized. The most recent jetty construc- 

 tion occurred in 1970. This inlet differs from most inlets on sandy coasts 

 because the sides of the channel are cut into rock formations. This has 

 limited the inlet cross-sectional area to about half the area that would be 

 expected for the tidal prism being admitted. Consequently, the inlet currents 

 are exceptionally strong and the littoral drift is carried a considerable 

 distance into the inlet. 



In 1962 a sand trap was excavated in a region where the inlet widens and 

 the currents decrease sufficiently to drop the sediment load (see Fig. 6-45). 

 This initial dredging produced 210,000 cubic meters (274,600 cubic yards) of 

 sand and rock, which was placed along the inlet banks and on the beach south 

 of the inlet. The trap was enlarged to 15 hectares (37 acres) in 1972 when 

 325,000 cubic meters (425,000 cubic yards) of sand and rock was removed. In 

 1978 approximately 143,400 cubic meters (187,600 cubic yards) of sand and 

 75,600 cubic meters (98,900 cubic yards) of rock were excavated, with the sand 

 being bypassed to the downdrift beach. 



e. Santa Barbara, California . The Santa Barbara sand-bypassing 

 operation was necessitated by the construction of a 850-meter (2,800-foot) 

 breakwater, completed in 1928, to protect the harbor (see Fig. 6-47.) The 

 breakwater resulted in accretion on the updrift side (west) and erosion on the 

 downdrift side (east). Bypassing was started in 1935 by hopper dredges which 

 dumped about 154,400 cubic meters (202,000 cubic yards) of sand in 7 meters of 

 water about 300 meters offshore. Surveys showed that this sand was not moved 

 to the beach. The next bypassing was done in 1938 by a pipeline dredge. A 

 total of 447,000 cubic meters (584,700 cubic yards) of sand was deposited on 

 the feeder beach area, which is shown in Figure 6-47. This feeder beach was 

 successful in reducing erosion downdrift of the harbor, and the operation was 

 continued by periodically placing about 3,421,000 cubic meters (4,475,000 

 cubic yards) of sand from 1940 to 1952 (Wiegel, 1959). 



In 1957 the city of Santa Barbara decided not to remove the shoal at the 

 seaward end of the breakwater because it provided additional protection for 

 the inner harbor. A small floating dredge was used to maintain the channel 

 and the area leeward of the shoal, which was occasionally overwashed during 

 storm conditions. Wave and weather conditions limited the dredging operations 

 to 72 percent of the time. 



In order to reduce the overwashing of the shoal, the city installed a 

 bulkhead wall along 270 meters (880 feet) of the shoal in 1973-74. The top 

 elevation of the wall is 3 meters (10 feet) above MLLW. This caused the 

 littoral drift to move laterally along the shoal until it was deposited 

 adjacent to and into the navigation channel. Since that time an estimated 

 267,600 cubic meters (350,000 cubic yards) of material per year has been 

 dredged from the end of the bar and the navigation channel. A part of this 



6-73 



