Cropley Soil Series
USDA Code: CA0121
K-Factor
0.37
Soil Erodibility Factor
Texture Class
clay
Drainage Class
moderately well drained
About Cropley
Deep, moderately well drained soils formed in alluvium from mixed sedimentary and crystalline rock sources. Vertic subgroup with high clay content (>35%) causing moderate to strong shrink-swell. Found on alluvial fans and terraces with slopes of 0 to 2 percent.
K factor values are sourced from the USDA Natural Resources Conservation Service (NRCS) SSURGO database.
Using Cropley 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
Widespread on the alluvial fans at the margin of San Francisco Bay in Santa Clara, Santa Cruz, and San Mateo counties. Historically a productive agricultural soil; now largely urbanized in Silicon Valley. Commonly encountered in geotechnical investigations.
Counties Where Found
Cropley soil FAQ
What is the K factor for Cropley soil?
Cropley has a listed K factor of 0.37 in the Rapid RUSLE soil directory. Confirm final values against project specific soil survey data before submitting permit documents.
Where is Cropley soil found in California?
Cropley is mapped in Alameda, San Mateo, Santa Clara, and other California counties. County mapping is based on available soil series data and should be verified for the exact project location.
How is Cropley used in RUSLE erosion calculations?
Use the Cropley 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 Cropley soil data
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