nc1: Horton method for composite Manning's n In iemisc: Irucka Embry's Miscellaneous Functions

Description

This function computes the composite Manning's n using the Horton method.

Usage

 1 nc1(P, 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 Horton method is

n_c = ≤ft[\frac{∑ \limits_{i=1}^N P_i n_i^\frac{3}{2}}{P}\right] ^ \frac{2}{3}

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.

Value

numeric vector that contains nc1 as Manning's composite n.

References

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

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.

n for Manning's n for natural channels, nc2 for Einstein and Banks 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.
 1 2 3 library("iemisc") # Example from the Moore Reference text nc1(n = c(0.05, 0.035, 0.05, 0.04), P = c(22.22, 34.78, 2.00, 6.08))