HR: 0800h
AN: OS21B-1220    [Abstracts]
TI: Modeling nearshore morphological evolution at seasonal scale
AU: * Ruggiero, P
EM: pruggiero@usgs.gov
AF: US Geological Survey, 345 Middlefield Rd MS999, Menlo Park, CA 94110 United States
AU: Walstra, D
EM: walstra@wldelft.nl
AF: WL|Delft Hydraulics, P.O. Box 177 , Delft, NL-2600 MH Netherlands
AU: Lesser, G
EM: glesser@usgs.gov
AF: US Geological Survey, 345 Middlefield Rd MS999, Menlo Park, CA 94110 United States
AU: Hanes, D
EM: dhanes@usgs.gov
AF: US Geological Survey, Pacific Science Center 400 Natural Bridges Drive, Santa Cruz, CA 95060 United States
AU: Gelfenbaum, G
EM: ggelfenbaum
AF: US Geological Survey, 345 Middlefield Rd MS999, Menlo Park, CA 94110 United States
AB: For the first time, process and nearshore bottom change measurements are being coupled along the dissipative, yet dynamic, beaches of the U.S. Pacific Northwest. A Spring 2001 field experiment on the ebb-tidal delta and adjacent beaches near Grays Harbor, Washington USA provides detailed information about bed sediments, waves, currents, suspended-sediment concentrations, and sea-bed change for the testing and improvement of numerical models of sediment transport and morphology change. Upwelling favorable winds from the NW predominated during the two-month deployment period which successfully captured the transition between the high-energy erosive conditions of winter and the low-energy beach-building conditions typical of summer. During the experiment onshore sandbar migration O(75m), trough infilling O(1m), and sub-aerial beach (shoreline) progradation O(10m) dominated nearshore morphological changes. However, over the four kilometer study area, significant alongshore variability in morphological response was observed. To investigate the mechanisms responsible for these observed morphological changes we are using a combination of data analysis techniques and numerical model simulations. Our specific research questions include: 1) What are the relative contributions of alongshore versus cross-shore processes in seasonal morphological change? and 2) What are the mechanisms responsible for the significant alongshore variability observed in both the sandbar and the shoreline response over only a few kilometers? A recently developed capacity to model cross-shore profile change (1DV) within an overall area modeling framework (2DH or 3D) is being applied to answer these questions. Model parameters are tuned by initially balancing onshore transports due to asymmetric oscillatory wave motion and offshore transport due to undertow along a series of individual cross-shore profiles. Area model results then allow us to explore the role of cell circulation and alongshore gradients in forcing not considered in 1DV modeling.
DE: 4219 Continental shelf processes
DE: 4255 Numerical modeling
DE: 4546 Nearshore processes
DE: 4558 Sediment transport
DE: 3020 Littoral processes
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting