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United States Department of Agriculture

Agricultural Research Service

Title: Vegetation and Soil Surface Cover Adjustments to Interrill Soil Erodibility on Rangeland

Author
item Weltz, Mark

Submitted to: Management of Landscapes Disturbed by Channel Incision Stabilization Rehabi
Publication Type: Proceedings
Publication Acceptance Date: May 23, 1997
Publication Date: N/A

Interpretive Summary: The USDA-Water Erosion Prediction Project (WEPP) is a new computer simulation program designed to estimate both sheet and rill erosion on rangelands Rangeland field experiments were designed to develop an adjustment to the soil erosion term as a function of canopy and soil surface cover. Data from twenty rangeland locations from across the western United States representing a wide range of soil and vegetation types were used to test the accuracy of the WEPP model under two scenarios: a) the existing rangeland option and b) using adjustments from the cropland option. Total soil loss from 120 rainfall events were compared with the WEPP model predicted soil loss. The results demonstrated that the current WEPP rangeland option under estimates sediment yield, while the cropland option significantly over estimates sediment yield on rangelands. A least squares optimization technique was used to improve the current erosion prediction equation in WEPP. The optimization procedure on the rangeland erosion adjustment factors did slightly improve estimates of soil loss. However, the model still under predicts soil loss on rangelands.

Technical Abstract: The USDA-Water Erosion Prediction Project (WEPP) is a technology based on fundamentals of hydrology, soil physics, hydraulics, and erosion mechanics. The WEPP model estimates erosion on uplands as a function of raindrop detachment and excess hydraulic shear in concentrated flow paths. Rangeland field experiments were designed to develop an adjustment to the baseline interrill soil erodibility equation as a function of canopy and soil surface cover. Twenty rangeland sites (120 plots)from a wide range of soil and vegetation types were evaluated using rainfall simulation techniques to test the WEPP model under two scenarios: a) the rangeland option and b) using adjustments from the cropland interrill erodibility equation. Total sediment yield values for each event were compared with the WEPP model predicted sediment yield. The results indicate that the current WEPP rangeland option under estimates sediment yield while the cropland option significantly over estimates sediment yield on rangelands. A least squares optimization technique was used in an attempt to improve the current interrill erodibility equation in WEPP. The optimization procedure on the rangeland interrill erodibility adjustment factors did slightly improve estimates of sediment yield.

Last Modified: 10/21/2014
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