Semester of Graduation
Master of Science (MS)
Geology and Geophysics
Coastal Louisiana is presently experiencing large amounts of coastal land loss with estimated rates exceeding 50 km2 lost per year. In an attempt to mitigate or reverse land loss, billions of dollars are earmarked for restoration projects that promote land reclamation, habitat stabilization, and defending against saline intrusion. This study was performed in an effort to better understand spatial trends of accretion rates in Barataria Basin in coastal Louisiana. Data for this project came from twenty-five shallow cores extracted over a broad span of the entire basin, from freshwater to saline environments. Cores were processed for 137Cs and 210Pb radiochemistry, bulk density, grain size, and organic matter measurements. The average vertical accretion rate (VAR) for the basin is 0.67 ± 0.14 cm/year and the average mass accumulation rate (MAR) is 1.58 ± 0.77 kg·m-2year-1. Vertical accretion rates from this study’s radiochemistry analysis agree with previous work in the basin (0.5-1.5 cm/year). Vertical accretion rates do not show a clear spatial trend but the mass accumulation rates shows sites south of Lake Salvador have larger values compared to those to the north. This dichotomy of trends suggests that paucity of mineral sediments does not inhibit marsh accretion in the northern area of the basin but that instead it is more reliant on the accumulation of organic material. Elevated mass accumulation rates in this study seem to overlap with the areas that historically have experienced the most land loss. It is hypothesized that material formerly comprising eroded marsh edges may be the source of this material, advected onto the marsh platforms during storm or inundation events. It was found here that hurricane sedimentation consists of 17.2 % of the mineral sediment inventory found across the basin. Fully contextualizing hurricane driven sedimentation requires more spatial data and analysis, however initial results presented here suggest that their presence is likely not the major source sustaining marsh elevations in Barataria Basin.
Shrull, Samuel Bryant, "Spatial Trends and Variability of Marsh Accretion Rates in Barataria Basin, Louisiana, USA Using 210Pb and 137Cs Radiochemistry" (2018). LSU Master's Theses. 4751.