K-Factor (Soil Erodibility Factor)

The K-factor is a standardized number, typically between about 0.02 and 0.69, describing how susceptible a particular soil type is to erosion from rainfall and runoff — higher values mean more erodible soil. It comes from the Universal Soil Loss Equation (USLE) and is published by the NRCS for most soil types.

K-factor is a direct input into sediment basin sizing: sites with highly erodible soil (high K) need proportionally larger basins, or additional BMPs, to control the extra sediment those soils shed.