285 



Although reliable figures showing the impact of solid wastes on the 

 estuarine environment are lacking, a situation from the San Francisco 

 Bay area is instructive : "In some instances, bay water has leaked into 

 old dumpsites ; when the tide goes out, black sludge is carried into the 

 water and hydrogen sulfide gas escapes into the air. In every dump, 

 even including those where no garbage is buried, an increase in 

 temperature plus an amount of decay produces hydrogen sulfide." 

 (IV-6-2.) In combination with salt water this produces a vile odor 

 that produces numerous complaints from residents near such dumps. 

 In short, the cost of cheap dumping of solid refuse despoils not only 

 the land surface to the west and the air for miles, but ultimately the 

 water quality of the bay itself. 



Such use has prohibitive impact because of the uncontrollable nature 

 and permanent damage cause by such activities. 



Bridges^ Jetties^ Dikes^ Breakwaters^ Causeways 



The prohibitive impact of such structures, when it occurs, is usually 

 far more gradual than the impact of large land fills. The group of 

 structures discussed here are either deliberately placed in an estuary 

 to control water movement or else cross the system to carry land 

 transportation. In either case they are long, narrow structures which 

 affect water movement patterns. Their effects may be beneficial to the 

 environment or they may be the reverse. 



The construction of a highway through the coastal area of Louisiana 

 and Mississippi effectively separated the inland areas of the coastal 

 marshes from the outer marsh areas, completely altering the circula- 

 tion patterns of the entire marsh system. The result has been saltwater 

 intrusion into the outer marsh system (in the absence of the fresh- 

 water inflow from inland sources now prevented by the highway), 

 with the subsequent results of soil alteration and eventual alteration 

 of the marsh vegetation (IV-6-3) . 



Such alterations may permanently change ecosystems and therefore 

 exclude the estuarine uses which depend on them. Commercial fishing 

 and sports fishing are particularly impacted by such changes. 



Shoreline Development 



Estuarine shorelines are extremely valuable for both commercial 

 and residential development. The shorelines of large cities are exten- 

 sively built up, primarily for navigation access and other commercial 

 development, but with considerable areas of shoreline drives and 

 residential developments. Nearly all of such kinds of development 

 extend up to, and sometimes beyond, the natural shoreline and 

 terminate in bulkheads, docks, or other permanent structures. 



The individual impact of such development is probably minimal 

 except in extremely confined areas, but the total effect of t\\^ shoreline 

 development of a large city can be to drastically and irretrie^^ably 

 change the natural environment, even to the extent of damaging the 

 uses for which the changes were made. 



Reduced currents and changes in water circulation may result in 

 increasing rates of sedimentation and added expense for channel 

 maintenance. 



Changes in circulation associated with both spoil disposal and manu- 

 factured residential islands in parts of Tampa Bay were followed by 



