138 



portant habitat has been lost; the largest single block of this has 

 been in the San Francisco Bay system, where much of the tidal marsh 

 and shallow waters no longer exist. 



The patterns of filling estuarine marsh and shallow water areas 

 closely parallel population and industrial development within the 

 estuarine zone. In North Atlantic and Middle Atlantic regions com- 

 mercial development has been the major cause of the filling of estua- 

 rine areas; in Florida (which has parts in three biophysical regions) 

 residential development has been the major reason for filling; in both 

 Louisiana and Texas dredging and filling associated with oil and 

 gas exploration has been the major cause for estuarine physical 

 modification. 



TABLE I V.2.10.— ESTUARINE HABITAT REMOVED BY DREDGING AND FILLING OPERATIONS 



Biophysical region 



Available habitat in 1955 (acres) 



Area of 

 total marsh 

 and wetland 



Area of 

 important wild- 

 life habitat 



Habitat lost, 1947-67 



Area dredged 

 and/or filled 



Percent of 

 habitat lost 



North Atlantic ..._ 168,000 



Middle Atlantic 424,000 



Chesapeake Bay 441,000 



South Atlantic. 1,551,000 



Caribbean (Florida only)... 469,000 



Gulf of Mexico.... 6,000,000 



Pacific Southwest 165,000 



Pacific Northwest 174,000 



Alaska (') 



Pacific Islands 10 



Total 9,392,000 



6, 175, 000 



565, 100 



7.0 

 8.6 



.5 

 2.3 

 7.5 

 4.8 

 67.0 

 4.0 



.2 



7.0 



> Insufficient data. 



References: USDI, Fish and Wildlife circular 39, "Wetalnds of the United States," 1956. USDI, Fish and Wildlife Service 

 data presented in congressional hearings, "Estuarine areas," House serial No. 90-3. 



Estuarine modifications due to control and regulation of tributary 

 freshwater streams may be unsought consequences rather than delib- 

 erate developmental schemes. Many of the Nation's major river basins 

 have been subjected to some type of major waste resource development, 

 as shown in table IV.2.11. These include flood control, public water 

 supply, power generation, or navigation projects. Generally, the more 

 densely populated and the more arid States have accomplished, out of 

 necessity, greater control of the surface water resources. 



California is investing over $2 billion to conserve the surplus water 

 in the northern half of the State and transport it to the southern half. 

 This great effort requires interbasin diversions from coastal basins and 

 results in much different fresh water inflow patterns in the estuarine 

 areas. Texas is also developing its water resources according to a care- 

 fully developed plan. Florida has built numerous flood control works 

 which have affected the drainage from Lake Okeechobee into the Ever- 

 glades and have altered the estuarine environment. The Savannah 

 Kiver in Georgia is fairly well-regulated by two upstream reservoirs. 

 The Eoanoke River in Virginia and North Carolina is regulated, as is 

 the Susquehanna in Maryland and Pennsylvania. There are numerous 

 control structures on small coastal streams in New Hampshire and 

 Oregon. 



