Supan Soil Series
K-Factor
0.32
Soil Erodibility Factor
Texture Class
loam
Drainage Class
well drained
About Supan
Deep, well drained soils formed in alluvium derived from basic volcanic rocks, principally andesite. Profile features a moderate argillic horizon. Found on remnant terraces and fans at 500–2,500 ft elevation on slopes of 2 to 30 percent.
K factor values are sourced from the USDA Natural Resources Conservation Service (NRCS) SSURGO database.
Using Supan in a RUSLE calculation
For a California construction project, use the soil K factor with rainfall erosivity, slope length and steepness, cover management, and support practice inputs. The K factor represents the soil erodibility portion of the model, so selecting the soil series that matches the site is important for defensible stormwater documentation.
In a SWPPP workflow, the practical question is not just what soil type is mapped near the project. It is whether the mapped series, K factor, and drainage assumptions match the site evidence well enough to support the RUSLE or RUSLE2 calculation.
California Distribution
Occurs in El Dorado and Amador counties on older, dissected alluvial surfaces derived from Mehrten Formation volcanics. Often associated with Aiken soils on adjacent uplands.
Counties Where Found
Supan soil FAQ
What is the K factor for Supan soil?
Supan has a listed K factor of 0.32 in the Rapid RUSLE soil directory. Confirm final values against project specific soil survey data before submitting permit documents.
Where is Supan soil found in California?
Supan is mapped in Amador, El Dorado. County mapping is based on available soil series data and should be verified for the exact project location.
How is Supan used in RUSLE erosion calculations?
Use the Supan K factor as the soil erodibility input in RUSLE or RUSLE2, along with rainfall, slope, cover, and support practice factors for the site.
Calculate erosion risk with Supan soil data
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