Environmental Aspects and System Types 



The gulf coastal refuges have a wide geog 

 of the Mississippi to the Coastal Bend area of 

 of climates from humid subtemperate to subhumi 

 affected by oil and gas activities include mar 

 brush-grass transition area, salt marsh, brack 

 marsh, as well as levees and spoil banks. Mos 

 refuge oil and gas in the U.S. has taken place 

 Louisiana. In addition there has been much al 

 channels, placement of spoil, and creation of 



raphic distribution from the mouth 

 Texas. This includes a range 

 d subtropical. The ecosystems 

 itime forest, coastal grassland, 

 ish marsh, fresh marsh, and delta 

 t of the development of coastal 



in the marshes of Texas and 

 teration of areas by dredging of 

 new land. 



The coastal areas of Louisiana and Texas have experienced extensive changes 

 as a result of man's activities. One of the larger projects has been the Gulf 

 Intracoastal Waterway. This canal parallels the entire coast, and possibly 

 only the Delta Refuge has not been directly affected by it. In other areas, 

 however, the dredging of this canal and the segmenting of marshes and bays with 

 spoil has led to changes in waterflow and circulation patterns. This has ulti- 

 mately resulted in alterations of the ecosystems as new balances of conditions 

 are reached. 



Other man-made activities which have had large-scale effects on the 

 refuges include: drainage of marshlands; construction of flood control struc- 

 tures; construction of agricultural water control areas; dredging of major 

 shipping lanes; channelization and "stabilization" of major river systems; and 

 alteration of the patterns of natural "intermittent extremes," such as occasional 

 flooding or fires, that were part of the functioning of many coastal ecosystems. 



All of the refuges under consideration have been affected by these activ- 

 ities. In addition, natural phenomena have had large effects on the area. 

 Hurricane Camille altered the Delta Refuge considerably. Other hurricanes may 

 have contributed to changes in vegetation on the Sabine Refuge. Erosion and 

 subsidence, two naturally occurring phenomena, were particularly evident at 

 some Louisiana sites. These processes may be accelerated by man's activities. 



The interplay of these natural and man-induced alterations produces large 

 effects which can be measured against the results of oil and gas extraction. 



Actual Methods Used 



Differences were noted in some of the actual methods used in oil and gas 

 operations. Some of the differences were due to contrasting ecosystems or 

 environmental conditions. For example, some marsh soils have such low bearing 

 strength that the only practical method of access is by canal. Roadways would 

 not have the strength to support heavy vehicles. 



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