Estimating the topographic factor in the universal soil loss equation for watersheds

ABSTRACT: A new, objective approach for estimating slope gradient and slope length frequency distributions for watersheds using topographic maps and Grenville9s spline function is described. Statistical analyses of slope segments and estimation of LS values for irregular slopes are used to analyze the computer-generated slope profiles and to produce the final LS values. The method was applied to 30 profiles in Ontario9s Lovers Creek watershed. Slope gradients and lengths also were measured in the field. Results of estimated values were compared with measured values to show the accuracy of the new method and the significance of the scale and contour interval of topographic maps.