The erosional threshold and shear strength of cohesive saltmarsh sediments depend on various factors, one of which is organic matter and the resulting aggregation of mineral particles. Field testing was conducted in Terrebonne Bay and Bay Jimmy to characterize the undrained shear strength and erosional resistance using a field shear vane (FSV) and a cohesive strength meter, respectively. In addition, laboratory testing was also performed on undisturbed tube samples to determine the erosional resistance. The organic matter content, root content, and salinity were also determined for the two sites, together with electron microscopy observations of the soil-organic matter aggregates. Results show that the critical shear stress increases with the organic matter and root contents. However, when the organic matter content (OMC) exceeds 10%, the critical shear stress decreases with OMC, as observed for the Terrebonne Bay sediments. This erosional resistance will also be discussed in terms of the degree of aggregation caused by organic matter that tends to bind soil particles.

Effects of organic matter on the aggregation and erodibility of saltmarsh sediment

245th National Meeting (2013)

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