problem that may be encountered in the overbuilding approach. Steep scarps 

 may develop at the toe of the fill as waves begin the readjustment, and these 

 scarps may make access to the beach difficult, as occurred in a California 

 beach-fill project constructed at Surf side and Sunset Beaches in 1979. The 

 scarping process may also increase erosion rates of the fill as large volumes 

 of sand avalanche into the littoral system when waves oversteepen or undercut 

 the fill slope. Scarping does not always develop but it can result more 

 easily when there is an abrupt transition between a steep fill slope and a 

 flatter natural offshore slope. 



The second approach, which may reduce scarping, is to initially place more 

 of the fill offshore. Redistribution of the sediment across the profile by 

 waves and currents will still take place after construction to reequilibrate 

 profile shape, but much of the reworking will occur offshore of the fill 

 rather than onshore. Using this construction approach, beach nourishment 

 projects in 1975 and 1977 at Rockaway Beach, New York, were conducted 

 hydraulically with the contractor's payment dependent on the amount of 

 material placed on the beach to the offshore depth where the 1:30 design slope 

 met the existing bottom. This approach also provided the contractor an 

 incentive to minimize his fill losses. In comparing the two approaches, the 

 offshore depth at Rockaway Beach ranged between 4 and 6 meters below MLW datum 

 versus depths of -1 to -3 meters mean sea level (MSL) for the overbuilt fill 

 sections at Carolina and Wrightsville Beaches in North Carolina. 



Both construction approaches result in an onshore fill section that is 

 placed to a desired berm width and has steep initial slopes. This onshore 

 fill eventually adjusts to a natural slope and narrows the berm, leaving the 

 impression that much of the fill has been lost, although it has only moved 

 offshore to reestablish a stable profile. 



f. Beach-Fill Transition . The alinement of a nourished beach segment 

 generally parallels the existing shoreline but is offset seaward by the width 

 of the fill. The nourished segment can be thought of as a subtle headland 

 that protrudes from the existing coast. Transition from the fill to the 

 existing shoreline can be accomplished either by constructing "hard" struc- 

 tures, such as groins and jetties, which compartment the fill or by filling 

 transition zones between the terminal ends of the beach fill and the 

 unrestored beach. 



Groins, jetties, and headlands do allow an abrupt termination of the beach 

 fill at the project limits. However, these hard structures are often quite 

 costly, unacceptable esthetically , and more importantly, they may interrupt or 

 modify the natural longshore transport flow in an area. If groins are 

 selected to terminate a fill. Chapter 5, Section VI should be used to 

 determine design components such as cross section, materials, and length. 



If filled transition zones are selected, their length and transition angle 

 will determine the additional volume of fill, and hence the cost, req_uired for 

 the project. The orientation of the transition shoreline will differ from the 

 natural shoreline alinement, resulting in different erosion rates since the 

 rate of littoral transport depends on the relative angle between the breakers 

 and a particular shoreline segment. 



5-22 



