A sampling of results and impacts from completed New York Sea Grant-funded research projects, written during the period February 1, 2009 – January 31, 2010
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The Size-Resolving Sediment Transport Model in the Upper Hudson River
R/CCP-15, Wang / Riemer / Flood
The present understanding of sediment transport in rivers and estuaries is insufficient to permit quantitative predictions of the fate of sediment particles. In order to improve the ability to model sediment transport and depositional patterns, circulation models need to be coupled with models that allow for the creation and destruction of flocs and subsequent changes in their settling velocity.
This project developed a coupled hydrodynamic-sediment transport model which allows for the creation and destruction of flocs and subsequent changes in their settling velocity.
The size-resolved flocculation model can predict the temporal evolution of the floc size distribution undergoing aggregation and breakup, and is verified with the published lab experiment results. The flocculation scheme has been successfully incorporated with the sediment transport component in a three-dimensional hydrodynamic circulation model (Princeton Ocean Model).
An idealized two-dimensional (in a longitudinal plane) study to simulate the Estuarine Turbidity Maximum (ETM) variations over tidal cycles has been carried out. The combination of gravitational circulation convergence and tidal asymmetry associated with settling flocs are primarily responsible for an ETM formation. Also, since lateral circulation can result in cross-channel transport of water mass and suspended sediments, an idealized three-dimensional simulation has been carried out to investigate the effects of lateral circulation on lateral trapping of sediments associated with flocculation processes.
Comparison with single-sized model experiment indicates that the traditional (non-flocculated) model approach cannot adequately represent the particle settling.
Finally, the three-dimensional model has been used to study the fine-grained sediment transport in the Upper Hudson River (Thompson Island Pool). The predicted sedimentation pattern and the deposition rate are in good agreement with the observed cohesive bed properties. The size-resolving, coupled threedimensional, hydrodynamic and sediment transport model resulting from this project is the first of its kind in the world, which represents a major advancement in modeling fine grained sediment transport.
The project also demonstrates the potential utilization of the model to address environmental issues surrounding the dredging in the Hudson River.
