caused impacts on the biological envi- 

 ronment. Among the effects of jetty 

 construction at Fire Island Inlet, the 

 following are easily predicted: turbid- 

 ity, destruction of benthic organisms, 

 reduction of species diversity and food 

 supply, release of toxic sediments, and 

 creation of new substrate (Carstea et 

 al. 1975a). The validity of these pre- 

 dictions could be questioned, however. 

 Additional study would be required to 

 discover site specific impacts. 



Jetties are designed to stabilize 

 inlets and, according to Kieslich and 

 Mason (1975), two objectives must be 

 considered. These are minimizing un- 

 desirable effects of wave action on nav- 

 igation channels and eliminating artifi- 

 cial maintenance of the channels. These 

 objectives do not, in any way, consider 

 biological impacts of the jetties. In fact, 

 no source of information was encounter- 

 ed which dealt with the physical or bio- 

 logical impacts of jetties. 



CASE HISTORY - BULKHEADS AND 

 ASSOCIATED DREDGING IN COASTAL 

 REGION 8 - GREAT LAKES 



In the Great Lakes region (Coastal 

 Region 8) there are a number of refer- 

 ences dealing with bulkheads, but very 

 few dealing with associated environmen- 

 tal impacts. Boberschmidt et al. (1976) 

 discussed environmental impact of small 

 structures in the Chicago District of 

 the U.S. Army Corps of Engineers. 

 They provided an analysis of a hypo- 

 thetical 200-ft (61-m) bulkhead on the 

 Fox River in Wisconsin which involved 

 no dredging. They also considered main- 

 tenance dredging at a commercial dock 

 on the Illinois River. Morton (1976) 

 has provided a comprehensive review of 

 the ecological effects of dredging. The 

 U.S. Army Corps of Engineers (undat- 

 ed)gives an excellent layman's introduc- 

 tion to shoreline protection structures 

 for the Great Lakes. Because of a lack 

 of specific information, only generaliza- 

 tions about the effects of bulkheads in 

 the Great Lakes are contained in this 

 case history study. 



Bulkheads are constructed in the 

 Coastal Region 8 to retain, or prevent 

 the sliding of, land and secondarily to 



protect the upland against wave dam- 

 age. Bulkheads also provide moorinq 

 facilities in many areas. Many unsatis- 

 factory methods of shoreline protection 

 may be employed prior to installation of 

 an adequate structure such as a bulk- 

 head (U.S. Army Corps of Engineers 

 undated) . 



Many possible construction alterna- 

 tives exist. They vary substantially in 

 cost. A wire mesh, woodpile, or sand- 

 bag bulkhead may cost no more than 

 $15 per linear foot (0.3 m), while a 

 steel bulkhead may cost as much as 

 $330 per linear foot (0.3 m) (U.S. 

 Army Corps of Engineers undated). 

 Among the construction alternatives 

 which may be considered in addition to 

 many types of bulkheads are revet- 

 ments, breakwaters, and groins. 



Construction impacts of bulkheads 

 are similar to those in other areas of 

 the country, including increased turbid- 

 ity and noise, reduced air quality, and 

 smothering of some organisms in the 

 backfill area. Resuspension of bottom 

 sediments will be greater when dredging 

 is associated with bulkhead construc- 

 tion. The use of diked disposal for 

 hydraulic dredge spoils results in sig- 

 nificantly less turbidity than many 

 other methods of disposal (Morton 

 1976). 



Bulkheads and seawalls are often 

 successful in providing immediate pro- 

 tection for areas in which no further 

 bluff recession can be tolerated, but 

 they frequently fail because of toe ero- 

 sion and back pressure (Michigan Sea 

 Grant Advisory Program undated). For- 

 ney and Lynde (1951) document a his- 

 tory of attempts to protect the P res que 

 Isle peninsula from erosion. 



The effects of bulkheads on coastal 

 processes are similar to those found in 

 other coastal regions. Erosion in adja- 

 cent areas which are not bulkheaded or 

 otherwise protected can sometimes be 

 expected. Littoral transport may also 

 be affected. A lack of dissipation of 

 wave energy can be expected on the 

 lakeshore during storms as compared to 

 the unbulkheaded beach (Boberschmidt 

 et al. 1976). 



127 



