Erodibility

Erodability (or erodibility) is the inherent yielding or nonresistance of soils and rocks to erosion. A high erodability implies that the same amount of work exerted by the erosion processes leads to a larger removal of material. Because the mechanics behind erosion depend upon the competence and coherence of the material, erodability is treated in different ways depending on the type of surface that eroded.

The most commonly used model for predicting soil loss from water erosion is the Universal Soil Loss Equation (USLE) (also known as the K-factor technique), which estimates the average annual soil loss ${\displaystyle A}$ as:

where R is the rainfall erosivity factor, K is the soil erodibility , L and S are topographic factors representing length and slope, and C and P are cropping management factors.

Other factors such as the stone content (referred as stoniness), which acts as protection against soil erosion, are very significant in Mediterranean countries.

Geological and experimental studies have shown that the erosion of bedrock by rivers follows in first approach the following expression known as the shear stress model of stream power erosion:

where z is the riverbed elevation, t is time, K_\tau is the erodability, ${\displaystyle \tau }$ is the basal shear stress of the water flow, and a is an exponent. For a river channel with a slope S and a water depth D, ${\displaystyle \tau }$ can be expressed as:

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