water pollution inevitably accompanies 

 construction activity. Petroleum pro- 

 ducts in minor quantities seep into the 

 water from construction equipment and 

 the exhaust emissions add hydrocarbons 

 to the air (U.S. Army Engineer District, 

 St. Paul 1976a). Turbidity can clog 

 gills of fish and other organisms. Toxic 

 materials and silt suspended by con- 

 struction activities can have a detrimen- 

 tal effect on the biota of the immediate 

 area (Morton 1976, Cronin et al. 1971). 

 Turbidity effects are most significant 

 upon juvenile stages and sessile organ- 

 isms. ' The dislodging of organisms can 

 cause a feeding spree by predators dur- 

 ing construction periods. 



Maintenance effects are much the 

 same as those resulting from construc- 

 tion, though often less severe. Break- 

 waters are constructed in high-energy 

 environments which are often character- 

 ized by sediments with fairly large par- 

 ticle size. Larce particle-size sediments 

 are less likely to cause turbidity or tox- 

 icity effects than are small particle-size 

 sediments characteristic of lower energy 

 environments. 



Chronic e ffects . After construction 

 is completed, a new situation exists both 

 at the breakwater and within the pro- 

 tected zone. Wave energy is much re- 

 duced inside the breakwater (Ortolano 

 and Hill 1972). A fixed breakwater can 

 cause piling-up of water behind it, de- 

 crease circulation, interfere with tides 

 and currents, and obstruct littoral drift 

 (Clark 1974, Sanko 1975). If the break- 

 water is shore-connected, particularly if 

 it has a shore-parallel leg, the effect 

 on littoral drift can be severe. 



Piling-up most frequently occurs 

 behind breakwaters that have restricted 

 openings. This leads to a higher water 

 level behind the breakwaters than out- 

 side (Diskin et al. 1970). Differences 

 in the water levels result in accelerated 

 flows at the openings or ends of a 

 breakwater. The resultant toe scour at 

 the base of the structure can cause 

 both local turbidity and damage to the 

 structure (Saville et al. 1965). 



Because of lower wave energy and 

 altered current patterns, the lee side of 



a fixed breakwater can experience de- 

 aradation of water quality and fluctua- 

 tions of temperature and salinity (Had- 

 erlie 1970). Sand tends to be deposited 

 on the shoreline opposite a detached 

 fixed breakwater and immediately updrift 

 of a shore-connected structure (Figure 

 12). The sand deposition opposite a de- 

 tached, fixed breakwater can form a tom- 

 bolo (a bar or spit that connects an is- 

 land with the shore) between the struc- 

 ture and the shore if the breakwater is 

 long enough in proportion to its dis- 

 tance from the shore (U.S. Army Corps of 

 Engineers 1973b). If conditions are not 

 conducive to tombolo formation, detach- 

 ed, fixed breakwaters can still cause 

 spit formation on the opposite shore- 

 line. This spit then acts as a partial 

 barrier to littoral drift, allowing the 

 sand to deposit updrift and be eroded 

 away downdrift. Floating breakwaters and 

 submerged breakwaters have much less in- 

 fluence on littoral drift (Harris and 

 Thomas 1974, U.S. Army Corps of Engi- 

 neers 1973b). 



Another problem which can occur 

 within a harbor partially enclosed with 

 fixed breakwaters is the generation of 

 secondary waves. These waves result from 

 reflection within a confined space and 

 can often attain considerable size and 

 energy (Saville et al. 1965). Careful 

 design will usually prevent this situa- 

 tion; but if it occurs, alterations in 

 the existing facilities become necessary 

 (Slawson 1977). 



Breakwaters constructed from the 

 rock, rubble, and other materials with 

 irregular surfaces provide a rocky surf 

 habitat on the seaward side, and a rocky 

 calm habitat on the lee side (Kowalski 

 and Poss 1975). These new habitats are 

 gained at the cost of the previously 

 existing bottom dwelling organisms. In 

 many situations, the new rocky habitat 

 can be considerably more productive than 

 substrate that previously existed. This 

 is well documented in literature about 

 artificial reefs. 



The protected water inside a fixed 

 breakwater, with the possible altered 

 fluctuations of temperature, salinity, 

 and water level, can lead to a change in 

 the plant and animal species composition 



22 



