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Restoration Success of Backfilling Canals in Coastal Louisiana Marshes

Authors

  • Joseph J. Baustian,

    Corresponding author
    1. Department of Oceanography and Coastal Sciences, Coastal Ecology Institute, Louisiana State University, Baton Rouge, LA 70808, U.S.A.
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  • R. Eugene Turner

    1. Department of Oceanography and Coastal Sciences, Coastal Ecology Institute, Louisiana State University, Baton Rouge, LA 70808, U.S.A.
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Address correspondence to J. J. Baustian, email baustian@lsu.edu

Abstract

The need for effective marsh restoration techniques in Louisiana is a pressing issue as the state continues to lose coastal wetlands. Returning spoil banks to canals, known as “backfilling,” is an attractive restoration option because it restores marsh, prevents future wetland loss, and is cost effective. The restoration of 30 canals backfilled 20 years ago was examined in this study and compared to restoration success 5 and 10 years after backfilling. Ultimately, the success of backfilling was controlled by the amount of spoil returned to the canal and the position of the canal in the marsh. Up to 95% of the spoil area was restored to marsh when the spoil banks were adequately removed, but only 5% of the spoil area was restored at sites where spoil removal was poor. Restoration of organic matter, bulk density, water content, and plant communities of the former spoil areas was also constrained by the adequacy of spoil removal. Backfilling restored up to 90% of the organic matter, 92% of the bulk density, and 93% of the water content after 20 years at sites where spoil was properly removed. Canals backfilled in areas of intact marsh showed greater restoration success than canals backfilled in highly degraded marshes. This study indicates that the benefits of backfilling continue to increase over time, although complete restoration will take longer than 20 years. Improving the completeness of spoil removal, coupled with appropriate site selection, could speed up the restoration process and enhance the success of future backfilling projects.

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