sediment-starved detached breakwater projects (Figures 10 and 15). In most 

 cases, beach fill should be considered a necessary part of the project plan. 

 Sediment size 



36. Sediment particle size and distribution affect longshore sediment 

 transport rates and the characteristic equilibrium beach profiles and, there- 

 fore, affect the shore planform and the rate of beach response. A breakwater 

 built offshore from a coarse-sediment beach will probably be in deeper water 

 than it would be for a finer sized sediment site because the coarse beach 

 equilibrium profile will be steeper. Waves approaching the coarse beach tend 

 to refract less because of the steeper offshore bathymetry; therefore, these 

 waves may reach the project at more oblique angles. Usually, a fine beach 

 will respond more quickly and attain an equilibrium shape sooner than a coarse 

 beach. A tombolo may develop on a fine sand beach, but the same incident wave 

 conditions might not cause tombolo development on a coarse sand beach. This 

 is due to greater wave energy in the lee of the structure, and lower volumes 

 of sediment transport on coarse, cobble beaches. Also, placed coarse sand 

 will probably not be lost from the project as rapidly as the native fine sand. 



Tombolos versus Salients 



37. Of great concern when designing a detached breakwater for shore 

 protection is whether or not the resulting shoreline should be or will be con- 

 nected to the structure. There are very different sediment transport patterns 

 associated with a tombolo than there are for a salient, and advantages and 

 disadvantages to each. 



38. Although the formation of either tombolos or salients may cause 

 erosion of neighboring shores, salients are usually preferred. Tombolo forma- 

 tion is more appropriate where the longshore transport regime is approximately 

 balanced, or where sediment loss from adjacent shores is not a concern. If a 

 detached breakwater is positioned seaward of the surf zone, or is long with 

 respect to its distance offshore, it can effectively shut off the prevailing 

 nearshore sediment transport, especially if a tombolo develops. Although 

 longshore transport may continue offshore of the breakwater, this sediment is 

 usually not immediately available to adjacent shores. The downdrift shoreline 

 may undergo drastic erosion until the longshore rate is restored. When a 

 tombolo forms, the large quantity of sediment which is impounded does little 



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