r.uslek
Computes USLE Soil Erodibility Factor (K).
r.uslek psand=name pclay=name psilt=name pomat=name output=name [--overwrite] [--verbose] [--quiet] [--qq] [--ui]
Example:
r.uslek psand=name pclay=name psilt=name pomat=name output=name
grass.script.run_command("r.uslek", psand, pclay, psilt, pomat, output, overwrite=False, verbose=False, quiet=False, superquiet=False)
Example:
gs.run_command("r.uslek", psand="name", pclay="name", psilt="name", pomat="name", output="name")
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]
--overwrite
Allow output files to overwrite existing files
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--qq
Very quiet module output
--ui
Force launching GUI dialog
psand : str, required
Name of soil sand fraction raster map [0.0-1.0]
Used as: input, raster, name
pclay : str, required
Name of soil clay fraction raster map [0.0-1.0]
Used as: input, raster, name
psilt : str, required
Name of soil silt fraction raster map [0.0-1.0]
Used as: input, raster, name
pomat : str, required
Name of soil organic matter raster map [0.0-1.0]
Used as: input, raster, name
output : str, required
Name for output USLE K factor raster map [t.ha.hr/ha.MJ.mm]
Used as: output, raster, name
overwrite: bool, optional
Allow output files to overwrite existing files
Default: False
verbose: bool, optional
Verbose module output
Default: False
quiet: bool, optional
Quiet module output
Default: False
superquiet: bool, optional
Very quiet module output
Default: False
DESCRIPTION
r.uslek calculates the USLE K factor, that is the Soil Erodibility Factor. It takes input of soil texture classes (sand, clay, silt) and organic matter, all in range of [0.0-1.0]. The FAO World Soil CD documentation 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 conversion 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
AUTHOR
Yann Chemin, SIC-ISDC, Turkmenistan
SOURCE CODE
Available at: r.uslek source code
(history)
Latest change: Friday Mar 07 07:39:48 2025 in commit e1e37d8