Exploratory Statistical Analysis of Controls on Sediment Bed Erodibility in a Partially-Mixed Estuary

Estuarine sediment erodibility is highly variable in both time and space and depends greatly on many sediment properties. Relationships between sediment properties and erodibility in pure mud sediments are better understood than sand-mud mixtures, the latter of which are prevalent in estuarine systems. Erodibility data, along with a suite of sediment and water column parameters were collected over 150 times at various locations along the York River Estuary, Virginia between 2005 and present. Sediment erodibility at these locations was evaluated using a Gust Microcosm. This apparatus measures erosion rate and critical stress for sediment erosion of a core which is carefully collected to preserve an undisturbed sediment/water interface. The microcosm uses a rotating disk to create a series of stresses from 0.01 to 0.6 Pa on the sediment surface within the core, which are stresses similar to the range commonly observed in partially-mixed estuaries from normal tidal and fluvial processes. Through exploratory data analysis, relationships between eroded mass as a function of bed stress and sediment and water column properties are being identified and evaluated using generalized linear models, generalized additive models, and principle component analysis. Factors being explored include grain size, percent moisture, organic content, tidal range, river discharge, sediment bioturbation and lamination, and fecal pellet abundance. Sediment x-rays for each core are sorted into structure categories including bioturbated, laminated, recently deposited, and sandy surface sediment. The preliminary results of this statistical analysis will be presented and discussed.