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PostPosted: Fri Dec 10, 2010 10:38 am 
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Joined: Mon Dec 28, 2009 4:01 pm
Posts: 39
Location: Ocean University of China
Dear ROMS users,

I want to user ROSM simulate the sediment transportation from coast to deep ocean. My domain is the whole East China Sea(117E-133E, 24N-41N), and the resolution is 10/60 degree. I know the importance of wave in suspending sediments at coastal area, so I need couple the SWAN model to simulate sediment transport. However, the User mannul of SWAN says that this wave mode is not recommended for ocean scale simulation.

I only expect the SWAN model could suspend coastal(depth <30m) sediments in this area when strong wind coming. I don't care about the wave character results. And the User Mannul also says that SWAN can be used on any scale relevant for wind-generated surface gravity waves. So can SWAN model suspend the coastal sediment correctly and not have bad effect to the current field on the ocean scale?

Thanks!


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PostPosted: Mon Dec 13, 2010 2:33 pm 
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Joined: Mon Aug 16, 2004 8:47 pm
Posts: 81
Location: U.S. Geological Survey, Woods Hole
One option is to use the SSW_BBL option in ROMS, and directly specify wave height and period throughout the domain, thereby avoiding SWAN. You can use simple wave formulas, for a given wind speed, fetch, and water depth to calculate the wave characteristics, and put those in a netcdf forcing file. SSW_BBL will read the heights and periods, and calculate the near-bed orbital velocity (Dean and Dalrymple), and the wave-current shear stresses (if either Madsen or Styles/Glenn wave-current interaction is also specified). These shear stresses will then be used to calculate sediment transport.

I used this method with idealized winds and it worked well for resuspending sediment during large events. If using in shallow water with large tidal range (for example, 2 m depths with 1 m tidal range), it will be important to make sure SSW_BBL uses total water depth (h+zeta) to calculate orbital velocity. I think the current version only uses "h" for the Dean and Dalyrmple formula. Below are the two studies where I used this method, if you need more information let me know. Good luck...

Ganju, N.K., Schoellhamer, D.H., and Jaffe, B.E., 2009, Hindcasting of decadal-timescale estuarine bathymetric change with a tidal-timescale model. Journal of Geophysical Research-Earth Surface, 114, F04019, doi:10.1029/2008JF001191.

Ganju, N.K., and Schoellhamer, D.H., 2009, Calibration of an estuarine sediment transport model to sediment fluxes as an intermediate step for robust simulation of geomorphic evolution. Continental Shelf Research, 29, 148-158.


-Neil


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