Author(s): Hem Raj Pant; Liming Hu; Guoping Zhang
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Keywords: Cohesive strength; Critical shear stress; Erosion; Organic matter content; Root content; Saltmarsh
Abstract: Coastal wetlands are the most productive ecosystem on Earth. The Northern Gulf Coast’s saltmarshes, one of the largest wetlands in North America, are undergoing severe land loss at an alarming rate, mainly due to erosion and subsidence, among others. The erosional resistance of cohesive sediments in the saltmarshes determines the wetland stability and sustainability. In this study, a cohesive strength meter was employed in the field and laboratory to measure the critical shear stress in an oil-contaminated saltmarsh and a non-oily normal saltmarsh. In addition, the variation of critical shear stress along the depth was measured for both sites. Results indicate that various soil properties (e. g., water content, organic matter content, root content, pore water salinity, particle size distribution) integratively affect saltmarshes’ erodibility. Yet, a clear understanding of the independent influence of these physical and geochemical properties on the erodibility of cohesive sediments requires further work. In general, a positive correlation exists between the critical shear stress and organic matter and root contents. The erosion threshold of the oil-contaminated sediment surface is less than that of the non-oily sediment, which may be attributed to the possibly reduced interparticle binding due to the residual crude oil retained within the pores of the cohesive sediments. However, an increase in the root contents below the ground surface in the oily sediments leads to better stability at depth than the non-oily sediments.
Year: 2013