In Situ Geotechnical Characteristics of Surficial Wetland Waterway Sediments

Abstract

Geotechnical surface sediment properties and behavior contribute to the success of wetland conservation and remediation actions, but the correlation between geotechnical sediment characteristics and active morphodynamics in such areas is still poorly understood. Therefore, a field investigation of surficial sediments was conducted in wetland waterways in the Terrebonne Parish, the St. Bernard Parish, and the Rigolets in coastal Louisiana. In situ tests were conducted at 29 locations using a portable free-fall penetrometer, supported by seven sediment core samples and data available from the literature. The results allowed the authors to map changes in sediment strength and stratification and discuss them with regard to local site characteristics, such as sediment type, abundance of vegetation, and vicinity to human-made structures and engineering activities, and to the local geomorphology. Stiff sediments were observed at submerged banks and bars. Two lakes differed significantly in their sediment-strength profiles, indicating differences in sediment-deposition history. Meandering resulted in an asymmetry of the geotechnical cross-channel profile. In summary, geotechnical sediment characteristics seem to reflect the inferred local sediment dynamics.