n_fischenich2000 {HYDROCAL}

Compute hydraulic roughness due to vegetation following Fischenich (2000)

Description

n_fischenich2000 calculate Manning's n using the Fischenich (2000) method for estimating vegetative roughness

Usage

n_fischenich2000(
  depth,
  hp,
  seperate = TRUE,
  Cd = 0,
  Ad = 0,
  CdAd = 0,
  restrict = TRUE
)

Arguments

depth

flow depth (H) in meters. Assumes wide channel geometry where depth is approximately equal to hydraulic radius.

hp

vegetation height (h_p) in meters. Vegetation is emergent.

seperate

Allows user to choose whether to use separate (Cd and Ad) or combined (CdAd). Type boolean. Default TRUE.

Cd

stand drag coefficient (C_d), default 0

Ad

vegetation area based on density (A_d), default 0

CdAd

Combined Cd and Ad values, default 0

restrict

allows for function parameters to restrict certain values. Type bool. Default TRUE.

Value

Manning's n

References

Fischenich, J. C. 2000. Resistance due to Vegetation. ERDC TN-EMRRP-SR-07, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi.

Fischenich, J. C., and S. Dudley. 2000. Determining Drag Coefficients and Area for Vegetation. ERDC TNEMRRP-SR-08, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi.

Examples

# Result: Manning's n of 0.100
n_fischenich2000(6,2,TRUE,0.955,0.755)

# Result: Manning's n of 0.059
n_fischenich2000(6,2,FALSE,CdAd=0.0199)

# Result: Manning's n of 0.090
n_fischenich2000(3,1,TRUE,0.1806,0.1662)

# Result: Depth must be positive.
n_fischenich2000(-1,1,TRUE,0.1806,0.1662)