Artificial Beaches . The establishment of beaches for re ^eational 

 and protective purposes has come into widespread use in the last fifteen 

 years. The protective effectiveness and stability of these beaches 

 depends on the beach width, berm height, and grain size oi" the beach 

 material. The degree to which a hurricane can cut back a beach and the 

 effect of placing sand on the beach of a different size from that normally 

 found thereon are samples of the questions that still need to be answered. 

 Numerous studies^ •^^»'^^' bearing on this problem of artificial beach 

 design and construction have been made, but additional work must be 

 done before the complete picture can be put together. 



Breakwaters and Jetties , Though properly considered as navigation 

 improvement structures, breakwaters and jetties sometimes have a 

 significant effect on the adjacent shores, A better understanding of 

 the short term as well as long term effects of these structures on the 

 adjacent shore lines is needed as many of the most severe and costly 

 erosion problems around out coasts have resulted from breakwater and 

 jetty installations which interrupt the littoral drift of sand along 

 the shore, A hydraulic model test of the broad aspects of this problem 

 is planned as a continuation of generalized tests of tidal inlets 

 now under way at the Waterways Experiment Station. The severe downdrift 

 erosion sometimes resulting from the installation of these structures 

 has led to the consideration of means of bypassing the impounded sand 

 past the breakwaters or jetties in order to maintain the downdrift 

 beaches; this is discussed in the next paragraph. 



Sand Bypassing Methods , The obvious need at some jettied inlets 

 and breakwaters to restore the normal littoral drift by bypassing the 

 impounded sand has led recently to the consideration of methods of 

 pumping the sand past the littoral obstruction. At least three 

 bypassing projects are now in operation in the United States, one at 

 Santa Barbara, California^ •^'^ » -^^^ , one at South Lake Worth Inlet, 

 Florida^^^^^, and one at Virginia Beach, Virginia. Three others are in 

 a trial status or under design for Port Hueneme, California, Lake Worth 

 Inlet, Florida, and Fire Island Inlet, New York, The design of these 

 installations is somewhat problematical at present, the main question 

 centering on what percentage of the net littoral drift can be reached 

 by a fixed pumping plant, a trestle-mounted plant, or a conventional 

 pipe-line dredge. It will probably be another four or five years before 

 a definitive understanding of the best design to fit a given situation 

 will be developed. 



Key Problems. Two problems which, if solved, would make the design 

 of shore protection works more reliable are: 



1. Given the total net littoral drift, determine the quantity 

 of sand being moved alongshore in various depth zones under selected 

 wave conditions. 



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