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 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

        r.usler, r.watershed

AUTHORS

       Yann Chemin, SIC-ISDC, Turkmenistan

SOURCE CODE

       Available at: r.uslek source code (history)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual