5r 



Figure 20. Segmented detached breakwaters showing the 



effects of varying the segment length and the number of 



gaps; near Rome, Italy (circa 1971) 



54. Combined response control techniques. The designer may use a com- 

 bination of the previous techniques to prohibit tombolo formation. The amount 

 and spatial variation of energy reaching the zone behind the breakwater is the 

 sum of transmission from (a) the ratio of structure length to distance off- 

 shore, (b) wave transmission through or over the structure, and (c) diffrac- 

 tion of wave energy through breakwater gaps. 



Location with respect to breaker line 



55. Placement of the breakwater landward of the normal breaker zone 

 will advance the shoreline and may cause tombolo development. When the break- 

 water is positioned well inside the breakers, a large percentage of the total 



45 



