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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.
Soil loss tolerance for a specific soil, also known as the T value, which can be calculated with [1] formula, is the maximum average annual soil loss expressed as tons per acre per year that will permit current production levels to be maintained economically and indefinitely. T values range from 1 to 5 tons per acre per year. [2]
Economic loss: the estimated costs for land degradation are US$44 billion per year. Globally, the annual loss of 76 billion tons of soil costs the world about US$400 billion per year. In Canada, on-farm effects of land degradation were estimated to range from US$700 to US$915 million in 1984.
The United States loses almost 3 tons of topsoil per acre per year. [16] 1 inch (2.5 cm) of topsoil can take between 500 [17] and 1,000 years [18] to form naturally, making the rate of topsoil erosion a serious ecological concern. Based on 2014 trends, the world has about 60 years of topsoil left.
The runoff curve number is based on the area's hydrologic soil group, land use, treatment and hydrologic condition. References, such as from USDA [ 1 ] indicate the runoff curve numbers for characteristic land cover descriptions and a hydrologic soil group. The runoff equation is: where. has a range from 30 to 100; lower numbers indicate low ...
T value. The United States Department of Agriculture defines the T Value as the maximum average soil loss (in tons per year) that will still allow economical maintenance of the current level of production into the future. [1]
It estimates the average annual soil loss A on a plot-sized area as: [98] A = RKLSCP. where R is the rainfall erosivity factor, [99] [100] K is the soil erodibility factor, [101] L and S are topographic factors [102] representing length and slope, [103] C is the cover and management factor [104] and P is the support practices factor. [105]
Soil erodibility is a lumped parameter that represents an integrated annual value of the soil profile reaction to the process of soil detachment and transport by raindrops and surface flow. [1] 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 ...