Sediment-transport modeling on Southern Californian shelves: A ROMS case study |
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| Authors: | Meinte Blaas Changming Dong Patrick Marchesiello James C McWilliams Keith D Stolzenbach |
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| Institution: | 1. Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, CA 90095-1567, USA;2. Department of Atmospheric and Oceanic Sciences, UCLA, Los Angeles, CA 90095-1565, USA;3. IRD, Brest, France;4. Department of Civil and Environmental Engineering, UCLA, Los Angeles, CA 90095-1593, USA;5. WL|Delft Hydraulics, Delft, The Netherlands |
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| Abstract: | Suspended sediment-transport processes in Santa Monica and San Pedro Bay are analyzed using the sediment-transport capabilities of the Regional Oceanic Modeling System (roms). A one-month simulation for December 2001 has been carried out with a set of nested domains. The model inputs include tides, winds, surface waves, and idealized initial sediment conditions for sand and non-cohesive silt. Apart from the control run, the sensitivity of the results to surface waves, ripple roughness and bed armoring has been analyzed. From the control experiment, the horizontal transport of sand turns out to be limited to within a few km of the nearshore erosion zones. During high wave events, silt is transported over further distances and also partly offshelf in distinct plumes. The effectiveness of horizontal silt transport depends strongly on vertical mixing due to both surface wind stress and wave-enhanced bottom stress. High wave events coincident with strong winds (hence strong vertical mixing) are the most optimal conditions for sediment-transport. Excluding wave effects in the simulation shows that surface waves are the dominant factor in resuspending bed material on the Southern Californian shelves. The sensitivity experiments also show that the direct influence of additional ripple roughness on erosion and deposition is relatively weak. Switching off bed armoring locally results in increases of near-bottom concentrations by a factor of 20 for silt and a factor of 5 for sand as well as stronger spatial gradients in grain size. |
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| Keywords: | Sediment-transport Wind waves Shelf sea circulation Wave boundary layer Santa Monica Bay San Pedro Bay |
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