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The Universal Soil Loss Equation (USLE) is a widely used mathematical model that describes soil erosion processes. [1]Erosion models play critical roles in soil and water resource conservation and nonpoint source pollution assessments, including: sediment load assessment and inventory, conservation planning and design for sediment control, and for the advancement of scientific understanding.
From the change in diameter of the hole over time, the rate of erosion can thus be plotted against applied hydraulic shear stress and fit to the following equation: [1] [4] = where E r is the rate of erosion over time, k d is the soil erodibility, and τ c is the critical shear stress for erosion.
The erosion index (EI, also called the erodibility index) is created by dividing potential erosion (from all sources except gully erosion) by the T value, which is the rate of soil erosion above which long term productivity may be adversely affected.
Few soil erosion models consider gully erosion, mostly due to difficulties in modelling these large erosional features. Several studies have evaluated the ability of soil erosion models to realistically predict measured rates of erosion, mainly on agricultural landscapes. There is often a wide discrepancy between predicted and observed erosion ...
[34] [35] There is growing evidence that tillage erosion is a major soil erosion process in agricultural lands, surpassing water and wind erosion in many fields all around the world, especially on sloping and hilly lands [36] [37] [38] A signature spatial pattern of soil erosion shown in many water erosion handbooks and pamphlets, the eroded ...
In its early stages of development, soil loss tolerance rates were inconsistent because they were obtained based on rough estimates. From 1961 to 1962, several groups of soil in the United States were designated with T rates ranging from 2 to 6 tons per acre per year. The rate was subsequently adjusted to 1 to 5 tons per acre per year. [5]
These soils have a very slow rate of water transmission (final infiltration rate less than 0.05 in (1.3 mm) per hour). Selection of a hydrologic soil group should be done based on measured infiltration rates, soil survey (such as the NRCS Web Soil Survey), or judgement from a qualified soil science or geotechnical professional. The table below ...
[22] [ambiguous] Calculations have suggested soil loss of up to 0.5 metres (20 in) caused by human activity will change previously calculated denudation rates by less than 30%. [23] Denudation rates are usually much lower than the rates of uplift and average orogeny rates can be eight times the maximum average denudation. [24]