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Impact of Bottom Friction coefficient

Thu, 12/12/2002 - 9:45am — JBlount
I am modeling a lake with a relative long residence time (~1 year). In the examples I have reviewed, the bottom friction values listed as part of the bathy files have ranged from 0.04 to 75. Questions is implementation of either the Chezy or Manning equations suitable or necessary when modeling a slow flow lake situation? What range of bottom friction values are typically input in the bathy files for long residence time lakes? Does turning on either the Chezy or manning flags overide the values input into the bayhy file? Thanks, Jon [addsig]
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Hydrodynamics
Tue, 12/24/2002 - 10:31am — Scott

Jon Keep in mind that the 0.04 is a Manning's friction factor and 75 is a Chezy factor - they are very different. For most lake or reservoir systems, you will find that they are not sensitive to the friction factor. You can use either Mannings (0.03 to 0.04) or Chezy (75). I would do a sensitivity analysis though to confirm that the model results are not influenced by the friction factor. Turning on CHEZY or MANN in the control file (w2_con.npt), forces the specification of friction in the bathymetry file. They must be compatible. Scott [addsig]