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increased shore erosion, removing more sediment than is contributed. 

 The primary pollutional problem from sediment, however, is from 

 increased influx and accelerated deposition. The detrimental effects 

 of sedimentation are reflected in an impairment of uses such as 

 navigation, recreation, and fish propagation. 



One of the greatest threats to the estuarine ecosystem is the ever- 

 present chance for a catastrophic spill of oil or other hazardous 

 materials. The large volumes of petroleum and chemical products trans- 

 ported through the estuarine zone by ships, barges, pipelines, tracks, 

 and railroads present a continuing opportunity for accidental bulk 

 spills. The consequences of these spills depend on the amount and 

 type of material released and the characteristics of the receiving 

 water. They may range in magnitude from tragic loss of life to little 

 more tnan economic loss for the transporter. 



The effect any pollutant has on an estuarine environment depends on 

 where it goes, how strong it is, and how rapidly it is assimilated 

 or flushed out of the environment. All of these conditions depend 

 on water movement and circulation patterns which are in turn governed 

 by tne relationship of tide and river flow to estuarine shane and 

 size. Physical modifications such as the dredging of new or deeper 

 navigation channels, ouilding of causeways or jetties, and even 

 construction of pier bridges can cause subtle changes in water move- 

 ment that can change the balance of environmental conditions in an 



