Manning's n values
Manning's n values
(OP)
Hello all - looking for reaction to the use of a Manning's 'n' value of 0.001 (yes, the decimal is in the right spot) to characterize the roughness of the surface of floodplain pools to be constructed in conjunction with a stream corridor restoration project. The weighted value of the pools with adjacent extensive riparian plantings (0.08 proposed) is 0.04 (or less) for the whole cross-section.
Beyond me how this value is physically possible in an engineered section, let alone a naturalized watercourse. Interested in other practitioners' reactions.
Thanks.
Beyond me how this value is physically possible in an engineered section, let alone a naturalized watercourse. Interested in other practitioners' reactions.
Thanks.





RE: Manning's n values
RE: Manning's n values
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: Manning's n values
You may find the USGS paper: "Guide for Selecting Manning's Roughness Coefficients for Natural Channels and Flood Plains" helpful: http://www.fhwa.dot.gov/bridge/wsp2339.pdf
In addition to methodology, this document contains photographs of various flood plains with associated known n-values. One may be able to find an example that is similar to your application.
RE: Manning's n values
RE: Manning's n values
RE: Manning's n values
RE: Manning's n values
I'm guessing here that you're trying to model numerous small pools that you're putting into a flood plain that would ordinarily be stagnant, but aren't during a flood. (?) Presuming that's the case, you should cut more sections, show the depth in the pool, and presume a roughness for the bottom of the pool. The fact that water moves easier over the pool will be modeled by the increased conveyance of that section, since the pool's area is counted in the cross section.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: Manning's n values
RE: Manning's n values
RE: Manning's n values
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com