Piezocone penetrometer measurements in coastal Louisiana wetlands

The importance of geotechnical properties and behavior of wetland soils is underscored by the many studies on wetland loss, e.g., marsh edge erosion, shallow subsidence, wetland collapse, and uprooting. This study provides an overview of using a modified piezocone penetrometer to rapidly evaluate marsh shear strength, porosity, and electrical conductivity over a range of ecological, geological, and hydrologic wetland conditions. Field campaigns were conducted in Terrebonne Bay near Cocodrie, Louisiana to evaluate the efficacy of the cone to characterize the shear strength and stratigraphy of salt marshes. Based on the field measurements, the test method was found to be repeatable and consistent with the ASTM D5778 standard guideline. The piezocone soundings were used to evaluate the shear strength and stratigraphy of the vegetation root mat, organic clay, and inorganic clay layers. These findings were synthesized into an idealized wetland geotechnical framework for developing mechanistic models of wetland loss.