HR: 11:40h
AN: OS21J-11    [PDF]
TI: Sediment Transport and Trapping in the Hudson River Estuary: a Tough Test for a 3-Dimensional Model
AU: * Woodruff, J
EM: jwoodruff@whoi.edu
AF: Woods Hole Oceanographic Institution, Department of Applied Ocean Physics and Engineering, Woods Hole, MA 02543 United States
AU: Geyer, W R
EM: rgeyer@whoi.edu
AF: Woods Hole Oceanographic Institution, Department of Applied Ocean Physics and Engineering, Woods Hole, MA 02543 United States
AU: Traykovski, P A
EM: ptraykovski@whoi.edu
AF: Woods Hole Oceanographic Institution, Department of Applied Ocean Physics and Engineering, Woods Hole, MA 02543 United States
AB: An estuarine turbidity maximum (ETM) resides within the Lower Hudson River estuary at intermediate salinities on the west side of the channel. Detailed water-column observations show that a strong salinity front persists within the ETM. A convergence of flow at the head of this front results in the focusing of suspended sediment, causing rapid accumulation under certain conditions. An acoustic altimeter recorded sedimentation rates as high as 1 cm per minute during a particularly intense trapping event. The magnitude of this sediment convergence is highly dependent on fortnightly variations in tidal amplitude. High tidal flows associated with spring tides enhance vertical mixing and intensify the front within the ETM. In addition, suspended sediment concentrations increase dramatically during spring tides. The observations indicate that the trapping occurs during the late stage of the ebb, when the near-bottom velocity behind the front drops below the threshold for resuspension. The observations collected from the Hudson ETM provide an excellent test-bed for a three-dimensional, sediment transport model. The Regional Ocean Model System numerical model (ROMS) is used to simulate the hydrodynamics within the Hudson River estuary and to assess the ability of a simple sediment transport scheme to reproduce the sediment transport regime observed within the Hudson. Model results show an inherent three-dimensionality in the mechanisms responsible for sediment transport and trapping within the ETM. During flood tide sediment is transported up-estuary, primarily on the deeper, east side. A transverse, secondary circulation sweeps sediment to the west side of the channel. During ebb tide, the model reproduces the observed salinity front within the ETM, and the pattern of sediment trapping is similar to the observations. A comparison of the observed and modeled deposition and erosion rates provides a challenging test of the model performance.
DE: 4235 Estuarine processes
DE: 4255 Numerical modeling
SC: OS
MN: 2002 Ocean Sciences Meeting