HR: 0800h
AN: H51D-0402    [Abstracts]
TI: Wave-Current Interaction and its Effect on Sand Transport at the Mouth of a Dynamic Estuary: Mouth of the Columbia River, OR
AU: * Lesser, G R
EM: glesser@usgs.gov
AF: Delft Hydraulics, PO Box 177, Delft, 2600 MH Netherlands
AU: * Lesser, G R
EM: glesser@usgs.gov
AF: US Geological Survey, 345 Middlefield Rd, MS999, Menlo Park, CA 94025 United States
AU: Gelfenbaum, G
EM: ggelfenbaum@usgs.gov
AF: US Geological Survey, 345 Middlefield Rd, MS999, Menlo Park, CA 94025 United States
AU: Moritz, R
EM: Hans.R.Moritz@nwp01.usace.army.mil
AF: US Army Corps of Engineers (Portland District), PO Box 2946, Portland, OR 97208 United States
AB: Regions of intense wave-current interaction are found near the mouths of most estuaries and are hypothesized to play an important role in the exchange of sediment between the estuary and the adjacent coast. Relevant processes include: 1) wave-driven currents due to radiation stress gradients and mass fluxes; 2) blocking and refracting wave energy by strong tidal currents; 3) enhancement of bottom boundary-layer turbulence, sediment entrainment, and apparent bed roughness by wave orbital motions; and 4) an increase in the vertical turbulent mixing and suspended-sediment carrying capacity of tidal currents due to the dissipation of wave energy. The Mouth of the Columbia River provides an excellent testing ground for our understanding of wave-current interaction, with tidal currents frequently reaching 3 m/s and offshore swell wave heights reaching 8 m. This study applies a three-dimensional baroclinic, process-based, sand transport model (Delft3D) to the mouth of the Columbia River. The model includes formulations for the wave-current interaction processes listed above and is tested against an extensive dataset collected during an August 2005 field experiment. During the experiment, instruments were located on five bottom-mounted tripods for a period of one month and roving ship-mounted instruments were sampled for 3 days along a transect that crossed the estuary . Instruments deployed include 4 ADVOs, 5 upward-looking current profilers, a downward-looking PCADP and ABS to precisely measure near-bed velocities and sediment concentrations, 10 OBSs, a LISST, numerous salinity-temperature and pressure sensors, and a P63 suspended-sediment sampling 'fish'. The model is used to investigate the role of wave-current interaction on sand transport in and around the mouth of the Columbia River and the role of waves and wave-current interaction in determining the net flux of sand between the estuary and adjacent shorelines is discussed. Model results identify a large region of the estuary entrance where both density effects on estuarine circulation and wave-current interaction have a significant effect on sand transport. The strengths and weaknesses of the model compared to the data from the field experiment are also presented.
DE: 1862 Sediment transport (4558)
DE: 4235 Estuarine processes (0442)
SC: Hydrology [H]
MN: Fall Meeting 2005