1 Oct 2020

Physical Factors That Influence Muddy Bed Aggregate Production, Size, and Durability

Abstract: Aggregation state significantly influences the transport characteristics of fine sediments. While research has documented the presence of mud aggregates in multiple coastal and estuarine environments, bed aggregates are largely absent from numerical models used to predict cohesive sediment transport. The U.S. Army Corps of Engineers (USACE) is conducting studies to evaluate the impact muddy bed aggregates have on sediment management issues, and how to account for aggregates in numerical models. In this study, physical properties associated with cohesive behavior were evaluated to determine if they could be used as predictors for bed aggregate production, size, and durability. Results showed that aggregates were consistently produced in cohesive sediments, and that median aggregate size was ~10-450x larger than the disaggregated sediment. Clay content had strong correlation with relative aggregate size, though statistically significant correlations were also found with sand content, water content, and density. Durability testing indicated that aggregate break-up followed exponential models, and that in limited instances, rates of break-up correlated with organic content.