and-after studies were made. Altered 

 currents within the estuary may have 

 caused changes in sedimentation, salin- 

 ity, and water temperature patterns. 

 Erosion probably eliminated some sandy 

 shore habitats, while accretion created 

 others. The jetties provide a substrate 

 for sessile and cryptic organisms and 

 fish communities associated with the 

 submerged structures. Turbidity, caused 

 by scour, may have affected organisms 

 in the area, and the confined channel 

 may be a less than optimum environment 

 for migrating smolts. 



In relation to the human environ- 

 ment, the presence of the jetties has ap- 

 parently enhanced the area as a beach 

 recreation and sport fishing area. Stabi- 

 lization of the entrance channel allows 

 fishing boats access to the harbor and 

 the sandy area behind the north jetty 

 provides clamming and fishing. The 

 jetties are extensively utilized by fish- 

 ermen. Erosion of the Bayocean Spit 

 has been blamed on the presence of the 

 north jetty, so the loss of habitat and 

 real estate may be a negative impact. 



Channel maintenance dredging, in- 

 clusion of weirs in jetties, bypassing of 

 sand, or no action at all are alterna- 

 tives to the construction of jetties such 

 as those of Tillamook Bay. If the inlet 

 is to remain navigable, the no-action 

 alternative is eliminated from considera- 

 tion. Channel maintenance dredging dis- 

 turbs the existing environment. Dispos- 

 al of dredge spoils on land or in the 

 estuary is generally considered unac- 

 ceptable and sea disposal preferable. 

 Thus, sand would be permanently lost 

 from the area. Sand placed on down- 

 drift beach would cause some temporary 

 loss of habitat of intertidal organisms, 

 but might slow erosion on the Bayocean 

 Spit. Turbidity and resuspended sedi- 

 ments could affect water quality. Fre- 

 quent dredging would be necessary and 

 costly. 



If an inlet must be stabilized, it 

 appears that no acceptable alternatives 

 to jetties exist. The impact of jetties on 

 the physical and biological environment 

 could be lessened by reducing their in- 

 terruption of littoral drift. Weirs, plac- 

 ed at intervals along a jetty's length, 



and bypassing of sand would serve this 

 purpose. This would reduce the erosion 

 of the shoreline downdrift and accretion 

 updrift. Whether the weirs would lead 

 to the necessity for more frequent chan- 

 nel dredging would require site-specific 

 study. 



Careful studies of potential effects 

 should be conducted before jetty con- 

 struction is begun. Too often an inlet 

 has been stabilized without thorough 

 knowledge of effects on other aspects of 

 the local environment. 



CASE HISTORY ■ 

 COASTAL REGION 

 CALIFORNIA 



BULKHEADS IN 

 2 - SOUTHERN 



Relatively little information was 

 available concerning the bulkheads in 

 Coastal Region 2, except some general 

 observations on the effects of bulkhead- 

 ina and the other protection measures 

 (Ploessel 1973, Carlisle 1977). 



Bulkheads and seawalls are used in 

 California for the same purposes as 

 elsewhere in the country. They contain 

 landfill and protect the bulkheaded 

 shoreline from erosion. They also pro- 

 vide mooring. 



Effects of bulkheads and seawalls 

 on the biota of California are not well 

 documented, but a high incidence of 

 red tide has been observed in harbors 

 which have poor water circulation as a 

 result of bulkheading (Carlisle 1977). 

 There is obviously a loss of habitat in 

 areas which are filled, and intertidal 

 communities may be severely affected if 

 a bulkhead is built below mean high 

 water. Scouring at the foot of a bulk- 

 head is a physical impact which affects 

 the benthic community in the vicinity of 

 the bulkhead. The vertical wall of the 

 bulkhead may also inhibit migration of 

 certain organisms from the water to the 

 shore (Carstea et al. 1975a) or along 

 the shoreline. 



Bulkheads and seawalls can have 

 significant effects on human use of an 

 area. Bulkheads in industrial or resi- 

 dential areas may increase boat traffic 

 by providing mooring facilities. Seawalls 

 on the open coast may restrict human 



112 



