required to prevent wave action from reaching improvements. Where the beach 

 is used for recreation, the justification for the increased width of the beach 

 may be governed by the area required for recreational use. Although there is 

 no current formally established standard in the United States, previous values 

 of 7 to 9 square meters (75 to 100 square feet) of dry beach per bather have 

 been used. Where the beach fill serves as a stockpile to be periodically 

 replenished, the berm should be wide enough to accommodate the recession 

 expected during the intervals between nourishment operations. 



e. Slopes . The toe of a stockpile of beach material should not extend 

 deeper than the effective limiting depth of sediment transport by wave-driven 

 longshore currents. Chapter 4, Section V,2,c can be used to calculate this 

 maximum depth. Also, the study of general offshore topographic relationships 

 provides estimates of this 9-meter depth below low water datum for eastern and 

 western seacoasts and about a 6-meter depth on the Great Lakes and gulf 

 coasts. The initial slope of any beach fill will naturally be steeper than 

 that of the natural profile over which it is placed. The subsequent behavior 

 of the slope depends on the characteristics of the fill material and the 

 nature of the wave climate. 



Design slopes are generally used for computing fill requirements since 

 natural processes are expected to generally shape the profile into an environ- 

 mentally equilibrated form. In practice, the initial foreshore slope of a 

 fill is designed parallel to the local or comparable natural beach slope above 

 low water datum. The design of the offshore slope should be determined after 

 careful investigation of all pertinent data from low water datxm to the appro- 

 priate offshore depth. The design slope is derived through synthesis and the 

 averaging of existing data within and adjacent to the problem area, and is 

 usually significantly flatter than the foreshore slope. Design slopes based 

 on such data are usually in the range of 1:20 to 1:30 from low water datum to 

 the intersection with the existing bottom. 



Construction slopes are seldom the same as design slopes because of the 

 working limitations of equipment used to place and shape the fill, and because 

 the selective sorting of the fill by waves and currents will naturally shape 

 the profile after nourishment. Two construction approaches are recommended. 

 One is to overbuild the upper part of the beach and the other approach is to 

 create an initial construction profile that extends significantly offshore. 



The "overbuilding" approach was adopted for fills at Carolina Beach in 

 1970 and Wrightsville Beach in 1981. This method places the required fill 

 volimie onshore at an elevation equal to the natural beach berm elevation 

 and has a fill slope that is steeper than the equilibrium design slope on 

 the seaward side. A part of the fill is placed underwater, in an amount 

 determined by the fill's berm width and seaward slope. Readjustment of the 

 fill sediments into a more equilibrated profile shape is accomplished almost 

 entirely by waves and currents that erode and redistribute the artificially 

 piled sediments and remove the finer unstable sizes through winnowing action. 

 In general, the fill volume placed should be adequate to establish the design 

 profile, after winnowing, and to provide an advance nourishment supply of 

 sediment. The total volume can be determined by using both the design draw- 

 ings and the calculated yearly rate of sediment loss from the beach, and by 

 applying the overfill ratio, R. , to these values in cases where the borrow 

 material to be used is dissimilar to native beach sediments. Scarping is one 



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