Cone Penetrometer Analysis of a Salt Marsh in Grand Bay, MS

Wetlands are valuable ecosystems that act as natural buffers, protecting coastal communities from storm surges, flooding, and erosion, supporting biodiversity and playing a role in carbon sequestration. Despite their small coverage on Earth's surface, wetlands are essential for ecological balance and biodiversity. Due to the shear amount of land loss occurring at coastal wetlands, this study was put in pieces to investigate the geotechnical and ecological characteristics, specifically soil shear strength, of marsh soils focusing on their role in shoreline stability and wetland resilience. Grand Bay estuarine was chosen as the study site since its unique characteristics and location on the Gulf of Mexico. Within Grand Bay two locations were chosen and each was divided into plots along a perpendicular transect to the shoreline. Various methods exist for measuring wetland shear strength, including direct shear testing, vane shear testing, and cone penetrometer testing (CPT). In this study, CPT was chosen for its ability to provide detailed in-situ measurements of soil strength and stratigraphy. The CPT data, combined with measurements of Dry Bulk Density (DBD) and Loss on Ignition (LOI), allows for a comprehensive assessment of soil stability and organic content. The results indicate variability in soil strength and composition across different distances from the shoreline. Higher values of sleeve friction near the shoreline reflect the dense root structures of vegetation, contributing to increased soil stability. Inland sites, with reduced vegetation density, exhibit lower values, indicating weaker soil. The DBD analysis shows increased values near the shoreline in 2023 compared to 2018, suggesting recent sediment deposition, likely influenced by storm surges. Meanwhile, LOI data reveals a decrease in organic matter content over time, indicating a shift toward more mineral-dominated sediments near the marsh edge. The findings from the study help in paving the way for future research for wetlands.