Hydraulic Roughness Coefficients for Native Rangelands

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 (r2=0.70) that incorporates the effect of raindrop impact, soil texture, random roughness, rocks, litter, and canopy and basal plant cover. The sites evaluated in the paper covered a wide range of vegetation types and included short‐, mi...

[1]  H. Barnes.  Roughness characteristics of natural channels , 1967 .

[2]  David A. Woolhiser,et al.  Simplifications of watershed geometry affecting simulation of surface runoff , 1977 .

[3]  John S. McNown,et al.  Runoff from Impervious Surfaces. , 1964 .

[4]  David R. Kincaid,et al.  Rainfall Effects on Soil Surface Characteristics Following Range Improvement Treatments. , 1966 .

[5]  Edwin T. Engman,et al.  Roughness coefficients for routing surface runoff , 1983 .

[6]  D. A. Woolhiser,et al.  Model Complexity Required to Maintain Hydrologic Response , 1988 .

[7]  M. A. Weltz,et al.  Rangeland experiments to parameterize the water erosion prediction project model: vegetation canopy cover effects. , 1991 .

[8]  F. R. Crow,et al.  Manning n and The Overland Flow Equation , 1977 .

[9]  J. Roels.  Flow resistance in concentrated overland flow on rough slope surfaces , 1984 .

[10]  Norris P. Swanson,et al.  Rotating-Boom Rainfall Simulator , 1965 .

[11]  R. A. Young,et al.  A Model to Estimate Sediment Yield from Field-Sized Areas: Development of Model , 1980 .

[12]  David A. Woolhiser,et al.  Unsteady, one‐dimensional flow over a plane—The rising hydrograph , 1967 .

[13]  R. Horton.  EROSIONAL DEVELOPMENT OF STREAMS AND THEIR DRAINAGE BASINS; HYDROPHYSICAL APPROACH TO QUANTITATIVE MORPHOLOGY , 1945 .

[14]  V. T. Chow.  Open-channel hydraulics , 1959 .

[15]  Cheng-lung Chen,et al.  Flow Resistance in Broad Shallow Grassed Channels , 1976 .

[16]  W. Graf.  Hydraulics of Sediment Transport , 1984 .

[17]  David A. Woolhiser,et al.  Unsteady one‐dimensional flow over a plane: Partial equilibrium and recession hydrographs , 1980 .

[18]  V. J. Palmer.  Retardance coefficients for low flow in channels lined with vegetation , 1946 .

[19]  Ruh-Ming Li,et al.  RAINFALL EFFECT ON SHEET FLOW OVER SMOOTH SURFACE , 1973 .

[20]  A. Parsons,et al.  Resistance to overland flow on desert hillslopes , 1986 .

[21]  H. Wheater,et al.  Evaluation of overland flow models using laboratory catchment data II. Parameter identification of physically based (kinematic wave) models , 1989 .

[22]  William W. Emmett,et al.  The hydraulics of overland flow on hillslopes , 1968 .