hyet_erosivity: Compute raifall erosivity

Description Usage Arguments Value Note References Examples

View source: R/hyet_erosivity.R

Description

prec_eros computes erosivity values using an hyetograph.

Usage

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hyet_erosivity(hyet, time_step, en_equation = "brown_foster")

Arguments

hyet

an hyetograph from hyet_create function. Precipitation values must be in (mm).

time_step

hyetograph's time-step in minutes. Must have one of the values: [5, 10, 15, 30].

en_equation

a character string specifying the equation to be used for calculating kinetic energy of rainfall. Must have one of the values: "brown_foster", "mcgregor_mutch", "wisch_smith". Default value is "brown_foster".

The rainfall's kinetic energy equations are:

  • Brown and Foster (1987),

    e = 0.29(1 - 0.72 exp(-0.05i))

  • McGregor and Mutchler (1976),

    e = 0.273 + 0.2168exp(-0.048i) - 0.4126exp(-0.072i)

  • Wischmeier and Smith (1958),

    e = 0.119 + 0.0873 * log10(i),

    with the upper limit of 0.283 MJ/ha/mm if i > 76 mm/h.

In the above equations i is rainfall intensity (mm/hr) and e is the kinetic energy per unit of rainfall (MJ/ha/mm).

Value

a tibble with values.

Note

hyet must not contain missing dates. Please use the hyet_fill function before using prec_eros.

References

Brown, L. C., & Foster, G. R. (1987). Storm erosivity using idealized intensity distributions. Transactions of the ASAE, 30(2), 379-0386.

McGregor, K. C., Bingner, R. L., Bowie, A. J., & Foster, G. R. (1995). Erosivity index values for northern Mississippi. Transactions of the ASAE, 38(4), 1039-1047.

Wischmeier, W. H., & Smith, D. D. (1958). Rainfall energy and its relationship to soil loss. Eos, Transactions American Geophysical Union, 39(2), 285-291.

Examples

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# load libraries
library(dplyr)
library(tibble)

# load data
data(prec5min)

# remove near zero values
prec5min$prec <- round(prec5min$prec , 1)

# compute EI
time_step <- 5
ei_values <- prec5min %>%
 hyet_fill(time_step) %>%
 hyet_erosivity(time_step)

 # filter erosivity events based on total rainfall height
 ei_values %>%
  filter(cum_prec >= 12.7)

kvantas/erosivity documentation built on July 25, 2018, 9:32 p.m.