Universal Soil Loss Equation

Universal Soil Loss Equation

Models of soil erosion 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. The most widely used soil erosion model is the Universal Soil Loss Equation (USLE) or one of its derivatives.

The USLE was developed in the United States based on soil erosion data collected beginning in the 1930s by the USDA Soil Conservation Service (now the USDA Natural Resources Conservation Service) [Wischmeier, W.H. and D.D. Smith. 1978. Predicting Rainfall Erosion Losses. A guide to conservation planning. Agriculture Handbook No. 537. USDA-SEA, US. Govt. Printing Office, Washington, DC. 58pp] [Wischmeier, W. H., and D. D. Smith, 1960. A universal soil-loss equation to guide conservation farm planning. Trans. Int. Congr. Soil Sci., 7th, p. 418-425.] . The model has been used for decades for purposes of conservation planning both in the United States where it originated and around the world, and has been used to help implement the United States' multi-billion dollar conservation program. The Revised Universal Soil Loss Equation (RUSLE) continues to be used for similar purposes.

The two primary types of erosion models are process-based models and empirically based models. Process-based (physically-based) models mathematically describe the erosion processes of detachment, transport, and deposition and through the solutions of the equations describing those processes provide estimates of soil loss and sediment yields from specified land surface areas. Erosion science is not sufficiently advanced for there to exist completely process-based models which do not include empirical aspects. The primary indicator, perhaps, for differentiating process-based from other types of erosion models is the use of the sediment continuity equation discussed below. Empirical models relate management and environmental factors directly to soil loss and/or sediment yields through statistical relationships. Lane et al. [Lane, L.J., E.D. Shirley, and V.P. Singh. 1988. Modeling erosion on hillslopes. p.287-308 In: M.G. Anderson (ed.) Modeling Geomorphological Systems. John Wiley, Publ., NY.] provided a detailed discussion regarding the nature of process-based and empirical erosion models, as well as a discussion of what they termed conceptual models, which lie somewhere between the process-based and purely empirical models. Current research effort involving erosion modeling is weighted toward the development of process-based erosion models. On the other hand, the standard model for most erosion assessment and conservation planning is the empirically based USLE, and there continues to be active research and development of USLE-based erosion prediction technology.

The USLE was developed from erosion plot and rainfall simulator experiments. The USLE is composed of six factors to predict the long-term average annual soil loss (A). The equation includes the rainfall erosivity factor (R), the soil erodibility factor (K), the topographic factors (L and S) and the cropping management factors (C and P). The equation takes the simple product form:A = R K L S C PThe USLE has another concept of experimental importance, the unit plot concept. The unit plot is defined as the standard plot condition to determine the soil's erodibility. These conditions are when the LS factor = 1 (slope = 9% and length = 72.6 feet) where the plot is fallow and tillage is up and down slope and no conservation practices are applied (CP=1). In this state:K = A/RA simpler method to predict K was presented by Wischmeier et al. [Wischmeier, W.H., C.B. Johnson, and B.V. Cross. 1971. A soil erodibility nomograph for farmland and construction sites. J. Soil Water Conserv. 26:189-193] which includes the particle size of the soil, organic matter content, soil structure and profile permeability. The soil erodibility factor K can be approximated from a nomograph if this information is known. The LS factors can easily be determined from a slope effect chart by knowing the length and gradient of the slope. The cropping management factor (C) and conservation practices factor (P) are more difficult to obtain and must be determined empirically from plot data. They are described in soil loss ratios (C or P with / C or P without).

ee also

*Erosion control

References


Wikimedia Foundation. 2010.

Игры ⚽ Нужно решить контрольную?

Look at other dictionaries:

  • Soil conservation — is set of management strategies for prevention of soil being eroded from the earth’s surface or becoming chemically altered by overuse, salinization, acidification, or other chemical soil contamination. The principal approaches these strategies… …   Wikipedia

  • Erosion prediction — Soil erosion prediction models play an important role both in meeting practical needs of soil conservation goals and in advancing the scientific understanding of soil erosion processes. They are used to help land managers choose practices to… …   Wikipedia

  • USLE — Universal Soil Loss Equation (Miscellaneous » Farming) …   Abbreviations dictionary

  • Usle — Este artículo o sección sobre medio ambiente necesita ser wikificado con un formato acorde a las convenciones de estilo. Por favor, edítalo para que las cumpla. Mientras tanto, no elimines este aviso puesto el 20 de mayo de 2009. También puedes… …   Wikipedia Español

  • RUSLE — est une abréviation pour Revised Universal Soil Loss Equation. C est un modèle empirique pour quantifier l érosion des sols qui reprend les termes de l USLE en corrigeant certaines inexactitudes. RUSLE calcule l érosion du sol selon une équation… …   Wikipédia en Français

  • USLE —   Sigles d’une seule lettre   Sigles de deux lettres   Sigles de trois lettres > Sigles de quatre lettres   Sigles de cinq lettres   Sigles de six lettres   Sigles de sept… …   Wikipédia en Français

  • Erosion control — is the practice of preventing or controlling wind or water erosion in agriculture, land development and construction. This usually involves the creation of some sort of physical barrier, such as vegetation or rock, to absorb some of the energy of …   Wikipedia

  • ÉROSION ET SÉDIMENTATION — L’histoire des continents résulte d’une évolution où interfèrent des forces internes nées de déséquilibres crustaux et des forces externes qui détruisent les constructions orogéniques édifiées par les premières. Tous les reliefs ne sont que des… …   Encyclopédie Universelle

  • Sediment control — A sediment control is a practice or device designed to keep eroded soil on a construction site, so that it does not wash off and cause water pollution to a nearby stream, river, lake, or bay. Sediment controls are usually employed together with… …   Wikipedia

  • Allgemeine Bodenabtragsgleichung — Mithilfe der Allgemeine Bodenabtragsgleichung (ABAG) lässt sich der zu erwartende mittlere jährliche Bodenabtrag einer Fläche durch Wassererosion als Schätzung ermitteln. Die ABAG lautet: A = R · K · L · S · C · P mit A: langjähriger, mittlerer… …   Deutsch Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”