Type of Document Master's Thesis Author Didier, Hannon URN etd-07112007-175513 Title Biogeomorphic Evaluation of Caminada-Moreau Maritime Beach Ridges with Respect to Future Restoration Initiatives Degree Master of Science (M.S.) Department Environmental Studies Advisory Committee
Advisor Name Title John White Committee Chair Ralph Portier Committee Co-Chair Irving Mendelssohn Committee Member Kevin McCarter Committee Member Margaret Reams Committee Member Keywords
- elevation gradient
Date of Defense 2007-06-25 Availability unrestricted AbstractRestoration efforts within the coastal zone of southern Louisiana have assumed greater importance in the wake of recent storms and ever increasing sea level rise. A poorly studied geomorphic structure known as the Caminada-Moreau maritime beach ridge complex exists along the southeastern Louisiana coastline between Grand Isle and the Port of Fourchon. Active subsidence in the area has reduced the overall elevation of these structures, decreasing the live cover of its most noticeable feature, stands of Quercus virginiana (live oak), along the ridge spines.
Elevation data was gathered along and across four randomly selected ridges in the study area with survey-grade differential GPS techniques. Calculated precision for these measurements, with respect to the base station, was ± 1.9 mm horizontally and ± 4.8 mm vertically (North American Vertical Datum 1988). Elevations in the study site ranged from 2.3 cm to 80.5 cm.
Moisture content, bulk density, pH, soil salinity, loss on ignition, total carbon, total nitrogen, and total phosphorus data were plotted against elevation data and modeled statistically. Significant negative correlations existed between elevation and all soil properties measured except pH and bulk density, which had significant positive correlations with elevation.
Plant species identification, cover data, height, and basal diameter were gathered at each surveyed and sampled location in order to determine species richness, dominance, and relative dominance. Species richness was plotted against elevation and statistically modeled, which resulted in a highly significant (p<0.0001), positive correlation (r=0.72). Dominance was used to produce a relevant species list from the original list of 25 identified species. As herbaceous species dominance decreased with increasing elevation, shrub dominance increased. Trees were only found in the highest elevation category.
These data can provide a guideline for future restoration initiatives in the study area. A restored ridge spine elevation of 1.6 m (NAVD 88) is recommended, taking into account local subsidence rates and sea level rise, mean elevation data for Quercus virginiana, and a project life of 100 years. A volume estimate of 1.6 million m3 of sediment may be necessary to restore all 27 km in the study site to the recommended elevation.
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