AN EVALUATION OF THE POTENTIAL FOR INFILLING EXISTING PIPELINE CANALSIN LOUISIANA COASTAL MARSHES

The impact of-canals and their dredged-material levees on Louisiana co astal marshes has been assessed in a number of studies. The aerial cov erage by canals and associated dredged-material levees has been shown to be approximately 10% of total marsh area in coastal Louisiana, whic h is about the same coverage as natural channels. In addition to the d irect loss of marsh habitat caused by the canals, the indirect effects of dredge material placement in levees has been associated with marsh deterioration. The restoration of productive fisheries habitat by inf illing pipeline canals depends upon maximizing the area of shallow wat er in the canals and restoring as much of the adjacent marsh habitat a s possible by removing dredged-material levees. The degree to which th e canal can be infilled depends upon the amount of dredged material av ailable and the bathymetry of the canal at the time of backfilling. Ge omorphic survey and analysis was used to evaluate the potential result of infilling canals and the type of habitat that may result. Comparis on of data for saline and brackish canal segments indicates that for b oth plugged and unplugged canals, canals in brackish areas have greate r potential for infilling than those in saline areas. However, older b rackish canals have a greater potential for the creation of shallow wa ter habitat than younger canals, suggesting that changes in canal cros s-section may be of greater magnitude than changes in levee material. Our analysis demonstrates that simple survey techniques can be used to indicate the potential efficacy of canal infilling. We recommend that such surveys be used to evaluate both pipeline and abandoned location canals across the Louisiana coastal zone to determine the potential f or increased shallow water habitat.