Water erosion estimation in topographically complex landscapes: Model description and first verifications

Two of the most important limitations when predicting soil movement are the natural complexity and the spatial heterogeneity of the processes. Sod erosion can vary significantly across short distances as a function of local soil properties and microtopography; but regardless of this, many erosion models assume homogeneity in topography and soil characteristics. The objective of this research was to develop a method for estimating soil loss from agricultural fields that is faithful to the complex topography and spatial heterogeneity common to managed landscapes. Sediment loss for individual storms was achieved by linking sod detachment-deposition equations adapted from the Water Erosion Prediction Project (WEPP) model to the existing water-flow subroutine in the Precision Agricultural-Landscape Modeling System (PALMS). In PALMS, sediment was routed appropriately in a two-dimensional grid, defining the pathways taken by the eroded material. Usually PALMS works on a grid-cell size of 5 to 20 m and simulates runoff and sod erosion patterns as affected by slope, soil texture, anisotropic surface roughness, soil consolidation, canopy cover, and tillage interactions with topography. In this study, PALMS and WEPP were used to simulate the sediment transport on an idealized field with a complex hillslope profile. Both models showed a consistent soil loss pattern and only minor differences in transport capacities. The models were also compared with data from actual erosion Plots, where both runoff and soil loss were predicted with similar errors for both PALMS and WEPP To illustrate the capability of PALMS, it was applied to a field with complex topography.