Mud matrix solids fraction and bed erodibility in the York River estuary, USA, and other muddy environments

Abstract

A 14-month time series of sediment cores from the bed of the York River estuary, Chesapeake Bay, USA, were sampled with a Gust erosion microcosm and further analyzed to evaluate variability in a variety of physical bed properties. Variation in sediment solids volume fraction did not relate to variability in bed erodibility. However, solids volume fraction was found to be highly dependent on the sand fraction of the bed. The solids volume fraction of the mud matrix was calculated to evaluate changes in bed compaction not related to the sand fraction of the bed. The range of variability in solids volume fraction of the mud matrix was found to be significantly less than the variability of the total solids volume fraction. Re-evaluation of erodibility data from the literature combined with that from this study revealed a strong correlation between solids volume fraction of the mud matrix and the initial critical stress for erosion when a large range in sand fraction and solids volume fraction were included. These results suggest that compaction within the cohesive portion of the bed is better related to erodibility than compaction of the bed as a whole (mud and sand). The poor correlation found within the York River data alone likely resulted from the relatively small range observed in the solids volume fraction of the mud matrix.