IV-436 



conditions preclude the large-scale use of such areas for purposes 

 other than navigation. 



The disposal of dredging spoil may also be a prhoibitive estuarine 

 use when it is deposited in other parts of the system or on adjacent 

 marshes or land. The destruction of habitat which can result from 

 such disposal will at a minimum remove the areas used for pro- 

 ductive participation in the estuarine ecosystem. 



The prohibitive impact of navigation dredging may, however, affect 

 an entire system, particularly where a major channel realignment or 

 channel deepening occurs. The prohibitive impact of such 

 modification may not be in direct destruction of habitat, but may 

 result from a change in water circulation patterns. 



For example, a change in current structure associated with channel 

 deepening in the James River prevented the upstream transport of 

 oyster spat to the beds where they normally settled and grew to 

 edible size (IV-6-1). 



Such prohibitive use impacts are not always associated with the 

 dredging of navigation channels; in fact, such activities can 

 enhance the environment by improving water circulation and crea- 

 ting new habitat. When there is an impact, however, it is prohibitive 

 in that it permanently excludes other uses while the channel exists. 



