Tuesday, November 14, 2006

Derivation of Terrain Factors Slope Length and Steepness of Revised Universal Soil Loss Equation (RUSLE) in a Geographic Information System (GIS) Environment.

Xu Yuan, John Havlin, David Crouse, and Rory Maguire. North Carolina State Univ, Dept Soil Science, PO Box 7619, Raleigh, NC 27695

Excessive P buildup in soil has become major agricultural non-point pollution. The Phosphorus Loss Assessment Tool (PLAT) was developed to evaluate the P loss potential in different pathways. While most parameters required are discrete data, many occur in spatial data formats that may enable the use of PLAT over variable spatial scales. The objective of this research is to evaluate the potential of using spatial data to estimate P loss. Preliminary results show PLAT outputs using elevation, soil type, and other spatial parameters in a Geographic Information System similar to those using field average data. An important parameter not directly available is the average annual soil loss, which is obtained by the Revised Universal Soil Loss Equation (RUSLE). We are evaluating the potential of obtaining a RUSLE estimate that would not require field assessment. Erosivity and Cropping Practice factors are constant over the field, but Erodibility, Slope Length (L), % slope(S), and Conservation Practice factors vary spatially. Our current efforts are developing an algorithm to estimate all necessary parameters, especially L and S using spatial data. Success of the GIS modeling will provide a valuable computer-based application of RUSLE. Further, it is essential to evaluate the potential of using PLAT spatially to estimate of P loss.