IV-561 



or inadvertently upsetting this balance. If upstream erosion is 

 increased due to poor land management practices, the load carried in 

 will increase. Conversely activities along the coast can result in 

 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 catas trophic spill of oil or other hazardous 

 materials. The large volumes of petroleum and chemical products 

 transported 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 than 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 the relationship of tide and river flow to estuarine shape 

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



