--- Welcome to the official ADCIRCWiki site! The site is currently under construction, with limited information. ---

For general information, see the ADCIRC site, ADCIRC FAQ, or the ADCIRC Wikipedia page. For model documentation not yet available on the wiki, see the ADCIRC site. New content is being continuously added to the ADCIRCWiki, and material from the main ADCIRC site will be gradually transitioned over to the wiki.

User:Taylorgasher: Difference between revisions

Jump to navigation Jump to search
No edit summary
No edit summary
Line 2: Line 2:

== test transclus ==
== test transclus ==
{{:Manning's n at sea floor}}
{{:Manning's n at sea floor#model specification}}

== test table ==
== test table ==

Revision as of 12:26, 4 September 2018

My user page

test transclus

The mannings_n_at_sea_floor nodal attribute is one of the available options for specifying bottom friction in ADCIRC based on the Manning formula. It is a nodal attribute in the fort.13 file, meaning that it allows spatially (and temporally) varying bottom friction in the model.

Attribute Summary

Drag coefficient contours for Manning's n and total depth

If the user elects to use this nodal attribute, which ADCIRC reads in as the ManningsN variable, NOLIBF must be set to 1 or the run will terminate. During execution, the Manning’s n values specified are converted to equivalent quadratic friction coefficients before the bottom stress is calculated. The equivalent quadratic friction coefficient is calculated according to the following formula at each node at each time step:


  • Cd drag coefficient
  • t time
  • g acceleration due to gravity
  • n Manning's n
  • h depth
  • η water surface elevation

The addition of the water surface elevation is conditional upon the setting of NOLIFA: η is treated as zero if NOLIFA = 0 in the fort.15 file. Finally, the value of CF in the fort.15 is used to set a lower limit on the resulting equivalent quadratic friction coefficient, under the assumption the Cd calculated from this formula tends to become too small in deep water.

Negative n Values

ADCIRC version: 55

If a combination of Manning's and time invariant bottom friction is desired, users can elect to set the Manning's nodal attribute to a negative value at certain mesh nodes. At mesh nodes where n is negative, the time invariant Cd coefficient, specified via a constant CF in the fort.15 file or the spatially varying quadratic_friction_coefficient_at_sea_floor fort.13 nodal attribute, will be used instead.

Specifying n Values

Manning's n is often assigned using land cover datasets, when available. Examples of commonly used land cover data in the US are the National Land Cover Dataset and the Coastal Change Analysis Program. There is a broad literature on specification of n values based on laboratory and fields studies, the most classical example of which is Chow (1959). Ideally, field surveys or review of on-site photography should be done to correlate land cover values to n. Alternatively, review of available literature may provide some basis for selecting values.

File Format


test table


apple pear
orange grape


ap ple
pe ar
ora nge
gr ape

Some norma text