to 60 years (Craig et cl. 1979). 



As a regional network, canals result in: (I) higher rates of wetland loss (Craig et 

 al. 1979); (2) increased saltwater intrusion, which further exacerbates the wetland loss 

 problem (Van Sickle et al. 1976); (3) changes in the hydrology of the wetland system 

 (Hopkinson and Day 1979, 1980a, 1980b; Craig et al. 1979; Kemp and Day in press); (4) a 

 reduction in capacity for wetlands to buffer the impacts of large additions of nutrients 

 (Hopkinson and Day 1979, 1980a, 1980b; Kemp and Day in press); (5) a loss in storm 

 buffering capacity; and (6) loss of important fishery nursery grounds (Turner 1977; Lindall 

 et al. 1979; Chambers 1980). 



Turner et al. (1982) have recently extended the analysis of the relationship of canal 

 density and wetland loss by examining U.S. Fish and Wildlife Service habitat maps for 

 1955 and 1978. The change in marsh as shown by 260 quadrangle mops in the deltaic 

 plain and the extent to which canals attributed to this change were examined. Again, a 

 strong relationship between canal density and wetland loss was found. Turner et al.( in 

 press) have estimated that if no additional canals were constructed in the wetlands, that 

 the loss rate would be 30 to 40 km^/yr less over the next 20 years. 



ADVANTAGES AND DISADVANTAGES OF DIFFERENT 

 MANAGEMENT OPTIONS FOR CONTROLLING WETLAND LOSS 



In managing the Atchafalaya River's contribution to wetland gain, a large area of 

 the Louisiana coast — from western Terrebonne Parish to the Texas border — will benefit 

 and a minimum amount of engineering aid will be required to accomplish land building. 

 The disadvantages are that this sediment nourishment is area-specific and does not seem 

 to be effective in flotant marshes (Baumann and Adams 1982). 



Controlled diversions of the Mississippi River have several advantages: (I) the 

 areas affected have high wetland loss rates; (2) there will be a possible improvement in 

 fisheries; and (3) advanced planning can be done and operational experience can be 

 gained. The disadvantages of controlled diversions are that: (I) they are area-specific 

 and can affect only the lower Mississippi River; (2) engineering costs are high; and (3) 

 there would be pollution problems associated with toxic substances in the Mississippi 

 River. 



Regulatory control over canals has the advantages of: (I) affecting all areas of the 

 coastal zone; and (2) addressing the major human cause of wetland loss. The 

 disadvantages are: (I) the opposition to such strict regulation by the political and private 

 sector; and (2) lack of complete information on the relationship between canals and 

 wetland loss. 



CONCLUSIONS 



Comparison of the effects of the different management options and mitigation 

 techniques for reducing wetland loss in Louisiana reveal that regulatory control of new 

 canals could reduce the loss rates approximately 30 to 40 km /yr, in contrast to 

 I to 3 km'^/yr for controlled diversion plans, and approximately 18 km /yr for land 

 building by the Atchafalaya River. If the problem of wetland loss is to be properly 

 addressed by regulatory agencies, they must make a serious attempt to control the 

 construction of canals (see Table I). 



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