Trojan Soil Series
K-Factor
0.24
Soil Erodibility Factor
Texture Class
gravelly loam
Drainage Class
well drained
About Trojan
Moderately deep, well drained soils formed in colluvium and residuum derived from basic volcanic rocks, primarily basalt and andesite flows. Found on volcanic plateaus and mountain slopes at 3,500–6,000 ft elevation.
K factor values are sourced from the USDA Natural Resources Conservation Service (NRCS) SSURGO database.
Using Trojan 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 Plumas and Sierra counties on volcanic terrain of the northern Sierra. Associated with ponderosa pine and mixed conifer forest; used for timber production and summer grazing.
Counties Where Found
Trojan soil FAQ
What is the K factor for Trojan soil?
Trojan has a listed K factor of 0.24 in the Rapid RUSLE soil directory. Confirm final values against project specific soil survey data before submitting permit documents.
Where is Trojan soil found in California?
Trojan is mapped in Plumas, Sierra. County mapping is based on available soil series data and should be verified for the exact project location.
How is Trojan used in RUSLE erosion calculations?
Use the Trojan 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 Trojan soil data
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