wetland areas as "flood control areas" 

 and preclude them from further agricul- 

 tural or urban development. 



An indication that such a system 

 can work in a mutually beneficial way, 

 at least on a small scale, can be found 

 in a number of crawfish ponds in swamp 

 habitat in the MDPR. These are all 

 impounded areas that are actively pumped 

 to prevent stagnation. The ponds are 

 flooded from September until the end of 

 the fishing season (May or June) and 

 then pumped dry. During the flooding 

 period, water is circulated through the 

 ponds on a regular schedule to maintain 

 high oxygen levels. This seasonal pat- 

 tern of summer drying and winter flood- 

 ing closely approximates the natural 

 hydrological cycle of the swamp. Stu- 

 dies have shown that these ponds main- 

 tain high water quality and swamp 

 productivity (Conner et al. 1981; Kemp 

 and Day 1931). The benefits of this 

 system include: (1) improved water 

 quality, (2) increased swamp produc- 

 tivity, (3) increased timber production, 



(4) improved wildlife habitat value, 



(5) increased crawfish production, and 



(6) reduced flooding. 



SALT WATER INTRUSION 



A number of management options have 

 been suggested to reduce the detrimental 

 effects of salt water intrusion in the 

 MDPR. Many landowners and management 

 agencies have argued for and sometimes 

 implemented impoundment or semi- 

 impoundment of wetlands as a means of 

 reducing salt water intrusion. The idea 

 is to surround low salinity marshs with 

 levees built of dredge spoil to limit 

 water exchange so as to protect the 

 impounded zones from encroaching salt 

 water. In the short term this approach 

 may be effective, although quantitative 

 studies to verify this are lacking. In 

 the long run, however, impoundment 

 reduces marsh grass productivity, 

 leading to the deterioration and loss of 

 the wetland being "protected." Impound- 

 ing prevents the exchange of nutrients 

 and sediments that are necessary for 

 maximum plant growth and marsh accretion 

 to offset subsidence. Two studies in 



the Barataria basin showed that sedi- 

 mentation in streamside marshes is suf- 

 ficient to maintain marsh elevation 

 against subsidence. Sedimentation on 

 inland marshes (like impounded marshes) 

 is insufficient, however, and many in- 

 land marshes are slowly turning into 

 open water (Delaune et al. 1978; Baumann 

 1980; Hatton 1981) . 



Studies have shown that hurricanes 

 impact impounded marshes to a much 

 greater degree than natural marshes 

 (Ensminger and Nichols 1957; Shiflet 

 1963). These studies indicate that 

 combatting salt water intrusion by 

 limiting marsh flooding is unwise. It 

 ultimately results in lower marsh pro- 

 ductivity, higher deterioration and land 

 lost, and greater susceptibility to 

 hurricanes. Another marsh management 

 strategy to reduce salt water intrusion 

 is to artificially increase the fresh 

 water input to a basin. Much less fresh 

 water currently enters the Barataria 

 basin than in the past, because of flood 

 control levees along the Mississippi 

 River. To the extent that canals in a 

 given area have increased the rate of 

 salt water intrusion, a restoration of 

 as much natural hydrology as possible 

 would help alleviate the problem. For 

 example, some canals could be perma- 

 nently closed, the cross-sectional area 

 of open canals could be reduced with 

 control structures, new canals perpen- 

 dicular to the coast could be discour- 

 aged, and locks could be considered for 

 major navigation channels. More infor- 

 mation, however, is needed on the hydro- 

 dynamics and use of different canals 

 and on the economic and ecological costs 

 and benefits of various alternatives. 



TOXIC SUBSTANCES 



Probably the most immediate envi- 

 ronmental management problem in this 

 country is the disposal of toxic sub- 

 stances, since this problem has such a 

 direct effect on human health and well 

 being. The MDPR is a national center of 

 the petrochemical industry, which con- 

 tributes large amounts of toxic 

 substances to the environment. Envi- 

 ronmental legislation in place has 



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