CONCLUSION 



There is strong indication that canal development is directly and indirectly related 

 to land loss rates. Causal mechanisms are still poorly understood, however. Canal 

 densities are not only increasing through time, but accelerating. As a result, land loss 

 rates are expected to increase as well. Since new canal dredging must now be permitted 

 by regulatory bodies, one might argue that regulatory action could influence further 

 canal density, and land loss rates. Perhaps fewer than a half-dozen of the first 2,000 

 dredging permits issued in 1981 by the Department of Natural Resources were denied 

 (although many are modified during review), and even these were subsequently approved 

 by the Secretary. Another solution might be to mitigate or minimize the damages of 

 existing and new canals. We have little data on the usefulness (or damage) of the various 

 mitigating techniques which have been suggested, such as weirs, backfilling, or spoil bank 

 design, for regional land loss reduction. River diversion schemes and current land 

 building in the Atchafalaya are locally important, but on a regional scale these could, at 

 best, reduce present total land loss rates by only 5% to 10% (Day and Craig 1982). 



State Senator Nunez asked at this conference, "Would there be a land loss problem 

 If we had no canals?" Although natural and artificial deterioration of older delta lobes 

 due to wave attack and the deficit of sediment accretion compared to subsidence and sea 

 level rise results in localized land loss, our analyses indicate that the direct and indirect 

 effects of canal development have greatly exacerbated the rate and geographic extent of 

 land loss in Louisiana. Furthermore, existing canals, through indirect mechanisms, will 

 continue to encourage significant wetland loss, compounding the effects of new canals. 

 With canals, the historic inevitability of local delta erosion and statewide gain is altered; 

 local erosion has expanded statewide, and there Is a net land loss of enormous magnitude. 



We have Inherited a truly major problem, but are doing little to solve it. Any 

 management plan that is to successfully combat coastal erosion on a meaningful level 

 must therefore address canal impacts and management. For example, increases in 

 barrier island erosion rates may be more symptomatic of the problem, than, as some have 

 argued, causal. As the area of wetlands behind the Islands erodes, more water Is flushed 

 In and out with each tide and storm. This enlarged tidal prism carries more salt water, 

 has greater system-wide currents, and alters sediment and water balances for plants that 

 bind the soil and barrier island dunes. The system-wide perturbation, caused by canals, 

 of estuarine salt balance, hydrology, sediment supply, and plants requires an integrated 

 study by a variety of experts. One grand experiment has been conducted for 90 years and 

 we can now see the results. Perhaps we can learn from it and proceed in a less damaging 

 manner in the future. The present attitude of the State of Louisiana seems to be that 

 the effect of canals Is ancillary or, at lease, not major. We estimate that canals are the 

 causal agents for at lease a majority (perhaps as much as 90%) of the present land loss, 

 yet the Joint Commitees of Natural Resources of the Louisiana Legislature (1981) 

 included no major programs for mitigation of canal effects among the $38 million In 

 projects recommended for the first phase of implementation of the Coastal 

 Environmental Protection Trust Fund Act. 



ACKNOWLEDGMENTS 



We thank E. Swenson for his comments, K. Westphal and C. Harrod for drafting the 

 figures, and Jo Paula Lantier for typing the manuscript. 



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