Effect of Elevation on Soil Properties in Reconstructed Back Barrier Island Coastal Marsh Using Dredged Materials

Abstract

Soil physical, chemical and bio-geochemical properties of a back barrier island coastal marsh restored by low pressure hydraulic dredging were monitored and analyzed from 2005 to 2009. A 109 ha restored marsh located at Port Fourchon, Louisiana, was divided into five habitats based on elevation. The habitats were classified as high (knoll), flat (swale), upper intertidal, intertidal and open water (submerged soils). The higher habitats were created nearer the dredged material source by deposited dredged coarser sediment mainly sand and oyster shells in mounds. Material with higher clay and silt content in the slurry were found in the habitats located at greater distances from the dredged material source. Soil elemental contents were statistically significantly different among habitats. Soil redox potential was also significantly different among habitats with the higher elevations having more oxidized redox values. Soil elevation was a strong influence on soil physical and chemical properties for several years post construction. Uneven distribution of dredged materials during the construction phase resulted in distinct variation in elevation and soil properties and the conclusion was that marsh creation would be more effective if dredged materials were uniformly distributed.

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