CSDMS 2011 annual meeting poster Ilgar Safak

Presentation provided during CSDMS annual meeting 2011

Modeling sediment transport processes and residence times in the shallow coastal bay complex of the Virginia Coast Reserve

Ilgar Safak, University of Virginia, Charlottesville Virginia, USA. ilgar@virginia.edu
Patricia Wiberg, University of Virginia, Charlottesville Virginia, USA. pw3c@virginia.edu

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Patterns of sediment transport and particle residence times influence the morphology and ecology of shallow coastal bays in important ways. The Virginia Coast Reserve (VCR), a barrier island-lagoon-marsh system on the Eastern Shore of Virginia, is typical of many shallow coastal bay complexes that lack a significant fluvial source of freshwater and sediment. Sediment redistribution within the bays in response to storms and sea-level rise, together with the dynamics of marsh and lagoon-bottom plants, largely governs the morphological evolution of this system. There are also important feedbacks between sediment and ecosystem dynamics. This is particularly true in the VCR, which is relatively unaffected by human activities. As a step towards evaluating the impact of hydrodynamics on sediment and ecological processes in the VCR, we employ a single unified model that accounts for circulation, surface waves, wave-current interaction, and sediment processes. This three-dimensional unstructured grid finite-volume coastal ocean model (FVCOM) is validated with field observations of wind- and tide-induced water flow (water level and current velocities) in Hog Island Bay, centrally located within the VCR. We present here the resulting patterns of sediment transport and particle residence times over event and seasonal time scales. Water and particle exchange within the VCR and between the VCR and the ocean is examined with the Lagrangian particle-tracking module in FVCOM. We focus on 3 bays with strongly varying bathymetry and coastline geometry, which are also located along a gradient of nitrogen input to the system. The results indicate that residence time of particles within the system vary greatly depending on the location of particle release, bay morphology, and wind conditions. The implications for morphologic evolution and ecosystem response to climate and land-use changes are evaluated.

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