IV-374 



bridges are frequently excellent fishing grounds, yet the same 

 piers can have adverse effects on water movement. 



A Public Health Service study of Great South Bay on Long Island, N.Y., 

 in 1961 found that water circulation west of the Bay Bridge was greatly 

 restricted, dye tracers showed that the bridge piers acted as a 

 partial barrier to water movement. Figure IV. 5. 12 shows the Bay Bridge 

 and schematically illustrates the movement of dye near the Bridge. 

 This study concluded that the restricted circulation west of the Bay 

 Bridge was a contributing factor to the degradation of water quality 

 in this area (IV-5-3). 



The insidious nature of environmental damage associated with physical 

 modification makes 1t difficult to assess and predict the effects of 

 specific physical changes on the estuarine environment. Three exam- 

 ples of the results of physical modification illustrate how flow 

 regulation can damage an estuary, what the results of progressive 

 filling can do, and how physical modification can improve the 

 environment. 



Charleston Harbor, South Carolina 



As part of the national plan to minimize unemployment during the 

 depression of the 1930's, the South Carolina Public Service 

 Authority was formed. Its purpose was to build a large dam, water 

 supply, flood control, navigation, and recreation complex that would 



