n_cowan1956: Compute hydraulic roughness following Cowan (1956)

In HYDROCAL: Hydraulic Roughness Calculator

Compute hydraulic roughness following Cowan (1956)

Description

n_cowan1956 calculate Manning's n using the Cowan Method (1956) for estimating total channel roughness

Usage

n_cowan1956(
  material,
  irregularity,
  cross,
  obstructions,
  vegetation,
  meandering,
  restrict = TRUE
)

Arguments

material	channel material (e.g. earth, rock cut, fine gravel, coarse Gravel)
irregularity	degree of bed irregularity (e.g. smooth, minor, moderate, severe)
cross	variations of channel cross section (e.g. gradual, alternating occasionally, alternating frequently)
obstructions	relative effect of obstructions (e.g. negligible, minor, appreciable, severe)
vegetation	vegetation (e.g. low, medium, high, very high)
meandering	degree of meandering (e.g. minor, appreciable, severe)
restrict	allows for function parameters to restrict certain values. Type bool. Default TRUE.

Value

Manning's n

References

Cowan, W. L. 1956. Estimating Hydraulic Roughness Coefficients. Agricultural Engineering. ASAE, August, 1956. Phillips, J. V., and S. Tadayon. 2007. Selection of Manning’s Roughness Coefficient for Natural and Constructed Vegetated and Non-Vegetated Channels, and Vegetation Maintenance Plan Guidelines for Vegetated Channels in Central Arizona. Scientific Investigations Report 2006–5108. USGS, Reston, Virginia.

Examples

# Result: Manning's n of 0.028
material <- 'Earth'
irregularity <- 'Smooth'
cross <- 'Gradual'
obstructions <- 'Negligible'
vegetation <- 'Low'
meandering <- 'Minor'
n_cowan1956(material,irregularity,cross,obstructions,vegetation,meandering)

# Result: Manning's n of 0.075
material <- 'Rock Cut'
irregularity <- 'Minor'
cross <- 'Alternating occasionally'
obstructions <- 'Minor'
vegetation <- 'Medium'
meandering <- 'Appreciable'
n_cowan1956(material,irregularity,cross,obstructions,vegetation,meandering)

# Result: Manning's n of 0.142
material <- 'Fine Gravel'
irregularity <- 'Moderate'
cross <- 'Alternating frequently'
obstructions <- 'Appreciable'
vegetation <- 'High'
meandering <- 'Severe'
n_cowan1956(material,irregularity,cross,obstructions,vegetation,meandering)

HYDROCAL documentation built on Feb. 16, 2023, 10:11 p.m.