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The Universal Soil Loss Equation (USLE) is a widely used mathematical model that describes 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 for sediment control, and for the advancement of scientific understanding. The USLE or one of its derivatives are main models used by United States government agencies to measure water erosion.〔National Resources Conservation Service, U.S. Department of Agriculture. Washington, DC. "Technical Assistance." 1996-06-04.〕 The USLE was developed in the U.S. based on soil erosion data collected beginning in the 1930s by the U.S. Department of Agriculture (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/Science and Education Administration, 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)〔United States Department of Agriculture - Agricultural Research Service. 2014. ("Revised Universal Soil Loss Equation (RUSLE) - Welcome to RUSLE 1 and RUSLE 2" ).〕 and the Modified Universal Soil Loss Equation (MUSLE) continue to be used for similar purposes. ==Overview of erosion models== 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 sedimentary 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Universal Soil Loss Equation」の詳細全文を読む スポンサード リンク
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