Validation of a 3-D enhancement of the Universal Soil Loss Equation for prediction of soil erosion and sediment deposition

A study was conducted on three U.S. military training areas to validate the Unit Stream Power Erosion and Deposition (USPED) model, a 3-dimensional enhancement to the Universal Soil Loss Equation (USLE). The USPED model differs from other USLE-based models in the manner in which it handles the influence of topography on the erosion process. As a result, the USPED model predicts both erosion and deposition, while most other USLE-based models are limited to predictions of erosion only. Erosion and deposition from a small watershed at Fort Hood, Texas, USA was quantified using ¹³⁷Cs, a radioactive isotope found in soils around the world as a result of fallout from post-World War II nuclear testing. We compared ¹³⁷Cs-derived erosion/deposition measurements with estimates derived from the USPED model and two applications of the USLE. Soil erosion and sediment deposition estimates generated by the USPED model were more accurate and less biased than results of the USLE applications. Both applications of the USLE consistently and significantly overestimated soil erosion; the USPED model did not. The USPED model was subsequently applied to Camp Guernsey, Wyoming, USA and Fort McCoy, Wisconsin, USA. Model estimates of soil erosion and sediment deposition were compared with field estimates of the same parameters. Based on 3 levels of soil erosion and 3 levels of sediment deposition, the model results agreed with field estimates 76 and 89% of the time at the two locations, respectively.