difficult to estimate. Whenever possible, on-site field tests of the proposed 

 structure(s) should be performed. Because of the large costs associated with 

 breakwater construction and even greater cost of modification, field tests may 

 prove to be cost-effective, especially for larger projects. A test structure 

 could be built or material could be added later to the prototype structure to 

 adjust the design through staged construction. 



87. For a single breakwater project, adjustment of the design could be 

 approached by constructing the breakwater so it is shorter than initially 

 designed and perhaps has a lower crest elevation to allow more overtopping 

 transmission. Shoreline response should be monitored for a suitable length of 

 time, at least two years. If the beach accretion is insufficient, the design 

 of the structure may be adjusted by lengthening the structure and/or raising 

 its crest elevation. This process may require several repetitions before a 

 suitable shoreline configuration is reached. The total construction cost for 

 the project probably would be significantly increased by the practice of field 

 modification; therefore, it may not always be practical. It is usually im- 

 practical to alter the orientation or increase the permeability of an existing 

 breakwater. 



88. If a long stretch of shoreline is to be protected by a segmented 

 breakwater, several test segments should be built, starting at the downdrift 

 end of the project or the area most in need of protection. The segments might 

 vary slightly in length, distance offshore, gap size, orientation, or even 

 crest elevation and permeability. The segment with the most satisfactory 

 shoreline response can then be used as the final breakwater design. When 

 judging the shoreline response to each segment, be wary of the effects of seg- 

 ment interaction, such as an updrift segment blocking the longshore sand sup- 

 ply to downdrift segments. Presque Isle, Pennsylvania, and East Harbor, Ohio, 

 are the only sites in the United States where breakwater field tests are pres- 

 ently being conducted in anticipation of a future, larger project. 



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