Hydraulic Roughness Coefficients for Native Rangelands

Abstract

A subfactor‐based regression technique for estimating hydraulic roughness coefficients for shallow overland flow was developed from simulated rainfall/runoff plots originally collected for erosion studies. The data were collected from 14 different native rangeland areas in the western United States. Rainfall was applied at a constant intensity of 65 mm/hr from a rotating‐boom rainfall simulator. Surfaces evaluated ranged from smooth bare soil to gravelly bare soil and sparsely to densely vegetated rangeland areas. A reference table of “effective roughness” coefficients for shallow overland flow is presented with a description of site characteristics. The derived roughness regression equations predict an “effective Darcy‐Wiesbach roughness coefficient” for native rangeland