r.uslek(1grass) GRASS GIS User's Manual r.uslek(1grass)
NAME
r.uslek - Computes USLE Soil Erodibility Factor (K).
KEYWORDS
raster, hydrology, soil, erosion
SYNOPSIS
r.uslek
r.uslek --help
r.uslek psand=name pclay=name psilt=name pomat=name output=name
[--overwrite] [--help] [--verbose] [--quiet] [--ui]
Flags:
--overwrite
Allow output files to overwrite existing files
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--ui
Force launching GUI dialog
Parameters:
psand=name [required]
Name of soil sand fraction raster map [0.0-1.0]
pclay=name [required]
Name of soil clay fraction raster map [0.0-1.0]
psilt=name [required]
Name of soil silt fraction raster map [0.0-1.0]
pomat=name [required]
Name of soil organic matter raster map [0.0-1.0]
output=name [required]
Name for output USLE K factor raster map [t.ha.hr/ha.MJ.mm]
DESCRIPTION
r.uslek calculates the USLE K factor, that is the Soil Erodibility Fac-
tor. It takes input of soil texture classes (sand, clay, silt) and or-
ganic matter, all in range of [0.0-1.0]. The FAO World Soil CD documen-
tation was used to produce the conversion system between soil textures
and soil classes. The soil classes are in number of 12 and apparently
come from a USDA publication of 1951 (p.209). Once the soil classes
have been identified (by vector cross-products tests), a general con-
version table was applied for transforming soil classes into K factor.
NOTES
r.watershed provides for USLE L, S, LS factors.
EXAMPLE
Calculate the USLE K factor (synthetic values, North Carolina sample
dataset):
# NC data: simulation
g.region rural_1m -p
r.mapcalc "sand = 0.11"
r.mapcalc "clay = 0.47"
r.mapcalc "silt = 0.42"
r.mapcalc "organ = 0.0136"
r.uslek psand=sand pclay=clay psilt=silt pomat=organ output=usle_k
r.univar usle_k
# Result: uslek = 0.25
Example with small variations (condition: d_sand + d_clay + d_silt =>
1.0)
# NC data: simulation
r.mapcalc -s "sand_r = rand(0.09,0.13)"
r.mapcalc -s "clay_r = rand(0.45,0.49)"
r.mapcalc -s "silt_r = rand(0.40,0.44)"
r.mapcalc -s "organ = rand(0.01,0.70)"
r.mapcalc "temp_sum = sand_r + clay_r + silt_r"
r.mapcalc "sand = sand_r / temp_sum"
r.mapcalc "clay = clay_r / temp_sum"
r.mapcalc "silt = silt_r / temp_sum"
r.mapcalc "test = sand + clay + silt"
r.info -r test
g.remove -f rast name=sand_r,clay_r,silt_r,temp_sum,test
r.uslek psand=sand pclay=clay psilt=silt pomat=organ output=usle_k
r.univar usle_k
# Result: uslek = variable values
SEE ALSO
r.usler, r.watershed
AUTHORS
Yann Chemin, SIC-ISDC, Turkmenistan
SOURCE CODE
Available at: r.uslek source code (history)
Accessed: unknown
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