SUMMARY OF LITERATURE 



BREAKWATERS 



Definition 



A breakwater is a structure offer- 

 ing wave protection to a shore harbor, 

 anchorage, or basin. Breakwaters are 

 usually "constructed to create calm wa- 

 ter in a harbor area, and provide pro- 

 tection for safe mooring, operating and 

 handling of ships, and protection for 

 harbor facilities" (U.S. Army Corps of 

 Engineers 1973b). 



Breakwaters may be further defin- 

 ed as fixed or floating, and shore-con- 

 nected or detached. Fixed breakwaters 

 are built up from the ocean, lake, or 

 estuarine floor while floating breakwa- 

 ters float at or near the water surface 

 and are held in place by a system of 

 tethers and anchors. Shore-connected 

 breakwaters have a connection to exist- 

 ing land while detached breakwaters are 

 not connected to the land. A detached 

 breakwater might also be called a paral- 

 lel or offshore breakwater. Shore-con- 

 nected breakwaters are structurally sim- 

 ilar to jetties, but differ in function in 

 that their primary purpose is to reduce 

 wave energy, not to maintain water 

 depth. Some structures function as 

 breakwaters and jetties. 



Figure 5 is a photograph of a con- 

 nected coastal breakwater which was 

 constructed to offer protection for a 

 natural harbor. Figure 6 is a photo- 

 graph of an offshore breakwater which 

 was constructed to create a harbor. 

 Figure 7 contains an example of a float- 

 ing breakwater. 



Structure Functions 



Probably the best known use of 

 breakwaters is to create or enhance 

 harbors for large or small craft. Nor- 

 mally these shore-connected breakwaters 

 extend into a body of water to provide 

 protection from waves caused by either 

 wind or passing vessels. Breakwaters 

 constructed to create a harbor may ad- 

 ditionally protect the shoreline from 

 erosion, alter longshore sediment trans- 

 port, and support pedestrian or vehicu- 

 lar traffic requiring access to deeper 



waters of a harbor or adjacent area. 



Detached breakwaters may be used to 

 prevent or reduce wave penetration into 

 a harbor entrance or to reduce the wave 

 attack on a costly structure, such as a 

 seawall or a power plant. Detached 

 breakwaters may also be used as sand 

 traps due to the tendency of sand to ac- 

 crete on the beach in the lee of the 

 breakwater. 



S ite Characteristics and Environmenta l 

 Conditions 



Shore-connected breakwaters often 

 have the connected end lying perpendic- 

 ular to the shoreline and the free end 

 lying parallel to the shoreline (Figure 

 5). In most cases, detached, or off- 

 shore, breakwaters are parallel to the 

 shore (Figure 6). Shore-connected break- 

 waters are placed according to site-spe- 

 cific functional requirements. Breakwa- 

 ters are most commonly used to provide a 

 sheltered harbor and, consequently, are 

 placed where they create an area with 

 minimum wave and surge action (U.S. Army 

 Corps of Engineers 1973b). When asso- 

 ciated with harbors and marinas, break- 

 waters usually define boundaries and 

 provide navigation channels, as well as 

 enclosing areas of lowered wave energy. 

 Because their primary function is energy 

 dissipation, breakwaters are usually 

 placed in high-energy environments, such 

 as coastal areas, semienclosed, or en- 

 closed bodies of water where there is a 

 long fetch or high occurrence of vessel- 

 generated waves. In at least one case, 

 however, breakwaters contributed to wave 

 resonance and caused considerable surge 

 within the harbor, resulting in boat 

 damage (Slawson 1977). Breakwater place- 

 ment is often determined by the exist- 

 ence of a shoreline area suitable for 

 harbor facilities rather than by bottom 

 topography, littoral processes, or other 

 factors. 



The biota of breakwater sites has 

 apparently had little study. No general- 

 izations can be made, based on existing 

 data, concerning bottom characteristics, 

 water quality, flora and fauna, or eco- 

 logical interrelationships at locations 

 where breakwaters have been planned or 



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