Sediment Loss and Transport Models

Erosion and sediment loss models have been developed based on the results of rainfall simulator studies and the use of experimental erosion run off plots (FAO, 2019).

• Rainfall simulators study the detachment of soil by raindrops; in simulated conditions, by varying the drop size and intensity of rainfall through nozzles, one can understand the impact of different precipitation events on different soil surface conditions.
• Erosion-runoff plots are sized at 22.1 m long and 4.1 m wide and have instruments located at the base of the plot where runoff and sediment can be captured and measured. Erosion plots can also be reliably used to assess the effect of management (such as tillage and cover) on soil loss.

Both the above studies were extensively used to develop the Universal Soil Loss Equation (USLE), one of the most widely used mathematical models to understand erosion processes. In the development of the first version of the USLE over 10,000 annual records from plots and small catchments were analyzed to develop the empirical relationships embodied in the equation (FAO, 2019). The USLE, developed in the US in the 1930s, was revised in 1993 to incorporate more advanced computerization and improved calculations leading to the Revised University Soil Loss Equation (RUSLE). Subsequently several other models have been developed based on similar principles but adapted on one or more parameters to account for improved data availability, differences in local geographic conditions or other specific requirements of the geographical area.