Model Behavior and Sensitivity in an Application of the Cohesive Bed Component of the Community Sediment Transport Modeling System for the York River Estuary, VA, USA

Abstract

Abstract:The Community Sediment Transport Modeling System (CSTMS) cohesive bed sub-model that accounts for erosion, deposition, consolidation, and swelling was implemented in a three-dimensional domain to represent the York River estuary, Virginia. The objectives of this paper are to (1) describe the application of the three-dimensional hydrodynamic York Cohesive Bed Model, (2) compare calculations to observations, and (3) investigate sensitivities of the cohesive bed sub-model to user-defined parameters. Model results for summer 2007 showed good agreement with tidal-phase averaged estimates of sediment concentration, bed stress, and current velocity derived from Acoustic Doppler Velocimeter (ADV) field measurements. An important step in implementing the cohesive bed model was specification of both the initial and equilibrium critical shear stress profiles, in addition to choosing other parameters like the consolidation and swelling OPEN ACCESSJ. Mar. Sci. Eng. 2014, 2 414 timescales. This model promises to be a useful tool for investigating the fundamental controls on bed erodibility and settling velocity in the York River, a classical muddy estuary, provided that appropriate data exists to inform the choice of model parameters.

Cohesive and mixed sediment in the Regional Ocean Modeling System (ROMS v3.6) implemented in the Coupled Ocean–Atmosphere–Wave–Sediment Transport Modeling System (COAWST r1234)

“…In this implementation, sediment deposited to the bed provided an easily erodible layer with an assumed low critical stress, τ c = 0.05 Pa. The modeled sediment bed erodibility and suspended sediment concentrations were both found to be sensitive to the parameterization of the equilibrium critical stress profile and to the consolidation and swelling timescales used (Fall et al, 2014). Here we present a case similar to that shown by Fall et al (2014), but that differs mainly in terms of the sediment bed initialization.…”

“…The modeled sediment bed erodibility and suspended sediment concentrations were both found to be sensitive to the parameterization of the equilibrium critical stress profile and to the consolidation and swelling timescales used (Fall et al, 2014). Here we present a case similar to that shown by Fall et al (2014), but that differs mainly in terms of the sediment bed initialization. The equilibrium critical stress profile was chosen as τ cb eq = z 0.62 p , which was a power-law fit to the erodibility experiments performed by Dickhudt (2008) on field-collected cores in September 2007 (Rinehimer et al, 2008).…”

“…As part of this program, colleagues have obtained complementary field observations there, which have been especially focused on the two locations off Gloucester Point and Clay Bank, VA (e.g., Dickhudt et al, 2009Dickhudt et al, , 2011Cartwright et al, 2013). The implementation presented here is similar to the three-dimensional model developed by Fall et al (2014) that accounted for circulation, sediment transport, and a cohesive bed. While this model neglects flocculation, information obtained by field observations such as the study by Cartwright et al (2013) • I tried to size this to fit in one-column of GMD (~3.5 in • I added an inset to locate the York within Chesapeake • I removed the red line that was across the Clay Bank t analyze anything along that transect.…”

“…We found that it was important to modify the sediment bed layering management scheme, as discussed in Sect. 5 below, to resolve the high gradients in bed erodibility evident in the sediment bed model (i.e., Fall et al, 2014) and data (i.e., Dickhudt et al, 2009Dickhudt et al, , 2011. In this implementation, sediment deposited to the bed provided an easily erodible layer with an assumed low critical stress, τ c = 0.05 Pa.…”

“…We have combined the approach of Sanford (2008) with biodiffusive mixing to represent depth-dependent changes in erodibility. This approach has been implemented in the cohesive bed stratigraphy algorithm in ROMS (described here) and applied by Rinehimer et al (2008), Butman et al (2014), and Fall et al (2014).…”