To prevent interference with natural onshore nourishment, beaches should 

 be nourished above MSL after most of the natural seasonal accretion has occurred 

 (September or October). It is also important, however, that fill be placed be- 

 fore the onset of fall and winter storms if the objective of fill is to form 

 a protective beach. Fill placed in early summer above the elevation of natural 

 summer accretion will not inhibit natural nourishment. Nourishment by dumping 

 in shallow water (< 10 feet) should be done in April or May to allow for the 

 maximum movement of the fill sand to the beaches by natural processes. The 

 amount this fill will interfere with the normal onshore sand movement is unknown. 



If stockpiling is used to nourish the beach, the best month for placement is 

 September for moving the material from north to south. For onshore movement and 

 retention on the beach, fill should be placed in the spring in a location where 

 it will not significantly interfere with the natural onshore movement of sedi- 

 ment. These criteria are not compatible. Thus, the selection of the time for 

 placement must be a compromise of the different factors that distribute the 

 material and of the design requirement, i.e., fill for recreational beach pur- 

 poses, for coastal protection, or for both. 



d. Loss Rates . An estimate of the short- and long-term volume fluctuations 

 in the fill material is important in designing a safe width for a protective 

 beach. It is difficult to predict the loss rates when using artificial fill. 

 Generally, the loss rates in fill material have been found to exceed those of 

 natural beach material at the same location even where the fill and native beach 

 sand sites are similar. For example. Everts, DeWall, and Czerniak (1974) foiond 

 loss rates for fill material placed in 1963 and 1970 at Atlantic City were much 

 larger than loss rates of adjacent natural material. When averaged over the 

 fill area, the I0S5 rates were 12 and 9 times the mean annual loss from the 

 entire subaerial beach. 



The volume loss rate as a function of shoreline retreat is required when 

 designing the width of a protective beach. Changes in sand volume above MSL 

 are closely related to changes in the MSL shoreline position. Figure 68 shows 

 sand volume change versus shoreline change between consecutive surveys. The 

 resulting correlation coefficient is given in Figure 69. Figure 70 illustrates 

 the ratio of volume change to shoreline change, averaged for each profile line 

 at Ludlam Beach. A shoreline change of 1 foot is accompanied by an average sand 

 volume change of about 3.6 cubic feet per foot. The range of values varies from 

 2.75 to 4.75 cubic feet per foot. The values are primarily a function of berm 

 elevation and foreshore slope. The higher the berm elevation and the greater 

 the average foreshore slope, the greater the volume loss or gain per unit re- 

 treat or advance of the shoreline. 



2 . Inlet Behavior . 



Inlets bounding Ludlam Beach are characterized by an erratic shoreline, 

 submarine bars, and shoal movements which typify inlets along sandy coasts. 

 Their capacity to trap sand moving alongshore in the littoral system or moving 

 onshore from seaward sources varies widely. Their capacity to provide sediment 

 to the adjacent littoral zones and offshore region also varies just as widely. 

 The pathline of sediment moving past Corson and Townsend Inlets also varies 

 with some sediment bypassing around the inlets on the seaward ebb tidal shoals; 

 other sediment moves into the inlet throat on the updrift side, then out again 

 onto the downdrift island shore. 



85 



