Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2003
Publication Date: 1/15/2004
Citation: Amore, E., Modica, C., Nearing, M.A., Santoro, V.C. 2004. Scale effect in usle and wepp application for soil erosion computation from three sicilian basins. Journal of Hydrology. 293:100-114. Interpretive Summary: Soil erosion prediction tools help society in many ways. They are used to help land managers choose conservation practices; as an engineering tool in the design of dams, reservoirs, channels, and other engineering structures; and for laws, policies, and regulations related to land use management. In recent years more emphasis has been placed on the use of process-based soil erosion prediction tools, primarily because they provide us with much more information than do older, statistically based models of erosion. Whereas older models, such as the Universal Soil Loss Equation (USLE), provided only information on soil loss, process based models such as the Water Erosion Prediction Project (WEPP) model provide detailed information on exactly where and when the soil erosion occurs, how much surface water runs off the land during storms, and where the sediment ends up after a storm. This study was undertaken to evaluate the accuracy of the WEPP model when applied to a semi-arid environment, in this case, in Sicily. The objective was to determine how well the model performed relative to the older USLE model. The results indicated that both models could be used to predict the erosion amounts, but that the USLE was generally easier to use and the WEPP model gave more detailed information regarding how, when, and where the sediment moved through the stream basins. The results of this study will help those who need to use soil erosion models choose the best model for a particular purpose.
Technical Abstract: Accurate estimation of soil erosion due to water is very important in several environmental matters, such us assessment of potential soil loss from cultivable lands and the evaluation of the decay of water storage capacity in reservoirs due to sediment deposition. Several studies have been carried out to build models suitable to quantify the results of erosion processes. These models, calibrated from experimental studies on plots or fields, have been applied at quite different scales. The aim of this paper is the application of two soil erosion models, with a distributed approach, to three large Sicilian basins upstream of reservoirs. Each basin is subdivided into hillslopes, using three different classes of average area, in order to estimate the scale effect on the sediment yield evaluation. The first model is the empirical USLE (Universal Soil Loss Equation), and the other one is the physically based WEPP (Water Erosion Prediction Project). A GIS is used as a tool to handle and manage data for application of the models. Values of sediment yield, computed with reference to different subdivisions, are compared with each other and compared with measurements of deposited sediment in the reservoir.