(2) Salient. Select a size for the salient that will provide 

 the desired average beach width without unacceptable 

 levels of recession behind the gaps. The ratio of segment 

 length to distance offshore should be between 2:3 and 1:2 

 for impermeable, nonovertopped structures. If the water 

 depth is too great, move the segments landward and in- 

 crease their permeability or overtopping characteristics. 

 Size the gaps according to the desired beach width oppo- 

 site each gap and the regional longshore drift. 



For nearly uniform protection over a long distance, use a 

 highly permeable, partially submerged, or frequently segmented 

 structure. 



(1) Connected shoreline. Uniform shoreline advance that con- 

 nects to the structure is not recommended because it would 

 block the nearshore sediment transport. 



(2) Unconnected shoreline. The structure length will be 

 slightly longer than the shoreline to be protected. Com- 

 pare the seasonal wave climate and shoreline positions to 

 obtain a gross estimate of the energy reduction required 

 to stabilize the shoreline in the desired position. Uni- 

 form shoreline advance is not possible if too much inci- 

 dent energy is blocked by the structure. This is par- 

 ticularly true for areas where the waves are seldom normal 

 to the shore and where there is significant gross long- 

 shore transport. Roughly 60 percent or more of the wave 

 energy should pass behind the structure. If the wave 

 direction is predominantly shore-normal and sediment move- 

 ment at the site is generally on/offshore, a greater per- 

 centage of wave energy can be blocked while still permit- 

 ting a uniform shoreline advance. The breakwater should 

 be located well outside the normal surf zone. There are 

 three methods that can be utilized to transmit wave energy 

 in this case. Wave overtopping is the least predictable 

 and least manageable method of wave transmission and 

 should not be used unless economic constraints deem it 

 necessary. Wave transmission due to structure perme- 

 ability is more feasible if artificial armor units are 

 used. The most predictable and practical method of uni- 

 form wave transmission is to build a highly segmented 

 breakwater. This is accomplished by making the segments 

 and gaps numerous and very short. The segments should be 

 impermeable and overtopped infrequently. The distance 

 offshore should be greater than eight times the segment 

 length to provide sufficient distance for the diffracted 

 waves to reorient themselves via refraction before reach- 

 ing the shoreline. Combining two or all three of the wave 

 transmission techniques is possible but highly complex 

 when used in a design. 



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