132, The efficacy and comparatively low total cost of shore protection 

 through placing and maintaining beach is predicated on the availability of 

 adequate supplies of beach material within economic pumping distance of the 

 beach. If suitable beach material is not readily available, some other 

 manner of protection may be requiredo Where projects are planned for long 

 periods, (say) 50 years, the total quantity of material, which would have 

 to be readily available, could conceivably approach 50,000,000 cubic yards, 

 depending on the rate of erosion or loss of material from the area, 



133« Protection by provision of widened beaches generally results in 

 low initial costs but comparatively high maintenance or replacement costs, 

 especially in the case of limited frontages. Other methods of protection 

 generally have higher initial costs, but often have lov;er apparent 

 annual charges. The choice must be made between high debt charges and 

 high maintenance costs. In manj instances a community may be willing 

 to bond itself for a high first cost, but the community's governing body 

 cannot comrait succeeding bodies to continuing maintenance costs. Where 

 maintenance is discontinued, either by choice or necessity, residual 

 protection after this time cannot be expected. Where annual costs of re- 

 plenishment may be excessive, the economic justification of groins to 

 reduce the rate of loss of fill should be investigated. Since maintenance 

 material placed at the updrift limit of an uninterrupted segment may 

 maintain the entire segment, the cost per unit length is usually comparatively 

 low for long reaches of shore. The method is therefore, most suitable for 

 large scale operations, rarely so for small scale operations, 



13U. Tidal Zone Slopes . - It is desirable to estimate in advance of 

 placement of a fill, the slope the fill may be expected to assume. Field 

 observations of existing beaches in the area or in neaiby areas should 

 always be made if possible} although complete data on offshore slopes are 

 lacking, some information is available on slopes in the vicinity of the 

 mid- tide line. Figure ^9 is a plot of slopes at approximately the mid- 

 tide line versus median grain diameter of the material at this point. 

 The median grain diameter of material which has been exposed to wave action 

 will ordinarily be coarser (due to selective transport by wave action) 

 than the median diameter of the material before placement. However, slopes 

 deduced on the basis of this last diameter may not be expected to differ 

 widely from ttiose based on the first diaraeter. As seasonal, storm or 

 other short term changes have been neglected in Figure 59, large but 

 temporary slope changes may be anticipated. To use the curves of Figure 

 59, the approxiinate foreshore slope may be read directly from the graph 

 based on the median diameter of the material available for placement. 



135«> Size of Beach Fills . - Basically, the two primary functions 

 of any placed beach fill are t.l) protection of upland areas and (2) 

 beneficial use of the beach fill, A beach deposit must be planned with 

 a residual width sufficient for recreational or other uses for which the 

 fill may be intended. This width will generally be established by the 

 city planner or other agency planning the development of the beach and 

 upland. If this width must be maintained, the protective fill must have 



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