Rising Water Levels in Coastal Louisiana: Implications for Two Coastal Forested Wetland Areas in Louisiana

William H. Conner, John W. Day, Jr.

Abstract


The coastal Barataria and Verret basins of Louisiana contain extensive areas of forested wetlands. Analysis of water gauge data in each basin reveals that apparent water level rise is 8.5 mm/year and 13.7 mm/yr for the Barataria basin and Verret basin, respectively. This high apparent water level rise is due mainly to regional subsidence. Sedimentation in the cypress-tupelo forests of Barataria basin is 6 mm/year versus 8.8 mm/yr in the cypress-tupelo forests of Verret basin. On the higher and drier bottomland ridge in the Verret basin, sedimentation is only 2.7 mm/yr. Apparent water level rise is greater than sedimentation in all areas leading to vertical accretion deficits of 2.5 mm/yr and 4.9 mm/yr in the swamps of Barataria basin and Verret basin, respectively, and 10.8 mm/yr on the bottomland ridge in Verret basin. This deficit is cumulative and is leading to a significant increase in the number of days flooded per year in each basin. If present trends continue, the forested wetlands in these basins will eventually be continually flooded and unable to reproduce themselves.


Keywords


Louisiana; subsidence; sea level rise; coastal forests; swamps; wetlands

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