A high erodibility implies that the same amount of work exerted by the erosion processes leads to a larger removal of material.
Other factors such as the stone content (referred as stoniness), which acts as protection against soil erosion, are very significant in Mediterranean countries.
[5][6] The K-factor is estimated as following [1][4] K = [(2.1 x 10−4 M1.14 (12–OM) + 3.25 (s-2) + 2.5 (p-3))/100] * 0.1317 M: the textural factor with M = (msilt + mvfs) * (100 - mc) mc :clay fraction content (b0.002 mm); msilt : silt fraction content (0.002–0.05 mm); mvfs : very fine sand fraction content (0.05–0.1 mm); OM: Organic Matter content (%) s: soil structure p: permeability The K-factor is expressed in the International System of units as t ha h ha−1 MJ−1 mm−1 Geological and experimental studies have shown that the erosion of bedrock by rivers follows in first approach the following expression[7] known as the shear stress model of stream power erosion: where z is the riverbed elevation, t is time, K
embeds not only mechanical properties inherent to the rock but also other factors unaccounted in the previous two equations, such as the availability of river tools (pebbles being dragged by the current) that actually produce the abrasion of the riverbed.
can be measured in the lab for weak rocks, but river erosion rates in natural geological scenarios are often slower than 0.1 mm/yr, and therefore the river incision must be dated over periods longer than a few thousand years to make accurate measurements.
[8] However, the hydrological conditions in these time scales are usually poorly constrained, impeding a good the quantification of D. This model can also be applied to soils.
An alternative model for bedrock erosion is the unit stream power, which assumes that erosion rates are proportional to the potential energy loss of the water per unit area: where
Relative differences in long-term erodibility can be estimated by quantifying the erosion response under similar climatic and topographic conditions with different rock lithology.