iemisc (version 0.9.9)

nc2: Einstein and Banks method for composite Manning's n

Description

This function computes the composite Manning's n using the Einstein and Banks method.

Usage

nc2(P, n)

Value

numeric vector that contains nc2 as Manning's composite n.

Arguments

P

numeric vector that contains "wetted perimeter of any section i"

n

numeric vector that contains "Manning's n of any section i"

Details

"A composite value of Manning's n for a single channel; that is, for the main channel only of a compound channel or a canal with laterally varying roughness." Source: Sturm page 118.

The equation to find Manning's composite n using the Einstein and Banks method is

$$n_c = \left[\frac{\sum \limits_{i=1}^N P_i n_i^2}{P}\right] ^ \frac{1}{2}$$

\(n_c\)

Manning's composite n

P

"wetted perimeter of the entire cross section"

\(P_i\)

"wetted perimeter of any section i"

\(n_i\)

"Manning's n of any section i"

N

"total number of sections into which the wetted perimeter is divided"

Source: Sturm page 118.

References

1. Terry W. Sturm, Open Channel Hydraulics, 2nd Edition, New York City, New York: The McGraw-Hill Companies, Inc., 2010, page 118-119.

2. Dan Moore, P.E., NRCS Water Quality and Quantity Technology Development Team, Portland Oregon, "Using Mannings Equation with Natural Streams", August 2011, http://www.wcc.nrcs.usda.gov/ftpref/wntsc/H&H/xsec/manningsNaturally.pdf.

See Also

n for Manning's n for natural channels, nc1 for Horton method for composite Manning's n, nc3 for Lotter method for composite Manning's n, and nc4 for Krishnamurthy and Christensen method for composite Manning's n.

Examples

library("iemisc")
# Example from the Moore Reference text
nc2(n = c(0.05, 0.035, 0.05, 0.04), P = c(22.22, 34.78, 2.00, 6.08))