Erosion prediction
Encyclopedia
There are dozens of erosion prediction models
. Most have been developed for agricultural areas and are design to compare predicted annual rates of soil
loss from broad areas under various cropland and rangeland
management techniques. Some are purely statistical
models, others mechanistic. Two of the more widely used methods in North America
are the Revised Universal Soil Loss Equation
(RUSLE) and Water Erosion Prediction Project erosion model (WEPP)
. Much of the research on erosion
rates is directed towards supporting or fitting these competing models. In particular much of the mineland
erosion literature is solely focused on fitting or improving RUSLE parameters. Aside from a few new deterministic gully erosion models, these models do not consider gully
erosion – mostly due to difficulties in modelling, and partly because gullies are often repaired in agricultural, forestry, or mining environments.
Because there is a wide discrepancy between predicted and observed erosion rates, models are better as research tools than as public policy and regulatory instruments or for prescriptive design measures for constructed landforms. But some models may provide useful guidance for the design engineer if adequately calibrated and verified for local conditions and if the design accounts for the uncertainty.
Most erosion modelling is applied to existing sites of known topography
and material properties to guide land management activities. Designers of constructed landforms, however, have considerable control over the topography, cover soil placement, initial revegetation, and to a lesser extent the substrate properties – flexibility that is generally uneconomical for farmers and ranchers and most users of erosion models. On the other hand, miners have little input into post-closure land use practices and management.
Methods to estimate erosion rates include:
Mathematical model
A mathematical model is a description of a system using mathematical concepts and language. The process of developing a mathematical model is termed mathematical modeling. Mathematical models are used not only in the natural sciences and engineering disciplines A mathematical model is a...
. Most have been developed for agricultural areas and are design to compare predicted annual rates of soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
loss from broad areas under various cropland and rangeland
Rangeland
Rangelands are vast natural landscapes in the form of grasslands, shrublands, woodlands, wetlands, and deserts. Types of rangelands include tallgrass and shortgrass prairies, desert grasslands and shrublands, woodlands, savannas, chaparrals, steppes, and tundras...
management techniques. Some are purely statistical
Statistics
Statistics is the study of the collection, organization, analysis, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments....
models, others mechanistic. Two of the more widely used methods in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
are the Revised Universal Soil Loss Equation
Universal Soil Loss Equation
The Universal Soil Loss Equation is a mathematical model used to describe soil erosion processes.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...
(RUSLE) and Water Erosion Prediction Project erosion model (WEPP)
WEPP
The Water Erosion Prediction Project Model is a physically based erosion simulation model built on the fundamentals of hydrology, plant science, hydraulics, and erosion mechanics. The model was developed by an interagency team of scientists to replace the Universal Soil Loss Equation and has been...
. Much of the research on erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
rates is directed towards supporting or fitting these competing models. In particular much of the mineland
Mining
Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...
erosion literature is solely focused on fitting or improving RUSLE parameters. Aside from a few new deterministic gully erosion models, these models do not consider gully
Gully
A gully is a landform created by running water, eroding sharply into soil, typically on a hillside. Gullies resemble large ditches or small valleys, but are metres to tens of metres in depth and width...
erosion – mostly due to difficulties in modelling, and partly because gullies are often repaired in agricultural, forestry, or mining environments.
Because there is a wide discrepancy between predicted and observed erosion rates, models are better as research tools than as public policy and regulatory instruments or for prescriptive design measures for constructed landforms. But some models may provide useful guidance for the design engineer if adequately calibrated and verified for local conditions and if the design accounts for the uncertainty.
Most erosion modelling is applied to existing sites of known topography
Topography
Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...
and material properties to guide land management activities. Designers of constructed landforms, however, have considerable control over the topography, cover soil placement, initial revegetation, and to a lesser extent the substrate properties – flexibility that is generally uneconomical for farmers and ranchers and most users of erosion models. On the other hand, miners have little input into post-closure land use practices and management.
Methods to estimate erosion rates include:
- purely statistical models
- subjectively determined erosion rates using expert judgement combined with a database of erosion rates of natural and reclaimed sites (natural and industrial analogs)
- surveying of existing erosional or depositional features of known age (or as determined by dating of deposits) to determine average erosion rates. Analysis of historical aerial photographs is often employed.
- site-specific empirical models that relate slope, watershedDrainage basinA drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...
size, and rainfall - empirical and semi-empirical or deterministic models based on laboratory and field flume measurements of erosion under simulated rainfall or flow conditions
- physically based gully erosion models
- landform and landscape scale models, often GIS-based, that apply erosion mechanics or statistical relationships to predict changes in topography and erosion rates
- sediment-budget models based on watershed monitoring.
External links
- "About the Universal Soil Loss Equation" - US Department of Agriculture