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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.
The jet erosion test (JET), or jet index test, is a method used in geotechnical engineering to quantify the resistance of a soil to erosion. The test can be applied in-situ after preparing a field site, or it can be applied in a laboratory on either an intact or a remolded soil sample .
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 ...
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 ...
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]
The term stream power law describes a semi-empirical family of equations used to predict the rate of erosion of a river into its bed. These combine equations describing conservation of water mass and momentum in streams with relations for channel hydraulic geometry (width-discharge scaling) and basin hydrology (discharge-area scaling) and an assumed dependency of erosion rate on either unit ...