n_cowan1956 {HYDROCAL}

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)