Roughness Coefficients for Selected Residue Materials

Abstract

Analysis of surface runoff on upland areas requires identification of roughness coefficients. A laboratory study is conducted to measure Darcy-Weisbach and Manning roughness coefficients for corn, cotton, peanut, pine needles, sorghum, soybeans, sunflower, and wheat residue. Varying rates of flow are introduced into a flume in which selected amounts of residue are securely attached. Roughness coefficients are calculated from measurements of discharge rate and flow velocity. The laboratory data are used to derive regression equations for relating roughness coefficients to Reynolds number and either percent residue cover or residue rate. Separate equations are developed for Reynolds number values from 500 to 20,000, and from 20,000 to 110,000. Generalized equations are presented for estimating roughness coefficients for other residue materials not used in this investigation. Accurate prediction of roughness coefficients for residue materials will improve our ability to understand and properly model upland flow hydraulics.

Impact of direct sowing mulch-based cropping systems on soil carbon, soil erosion and maize yield

“…Small quantities of crop residues are sufficient to form protective barriers on the soil surface that hinder surface runoff. These barriers act as 'microdams' that make water flows more sinuous and, consequently, increase the potential for water to infiltrate into the soil (Gilley et al, 1991). Besides, the 'microdam' effect reduces the kinetic energy of water flows, which diminishes the solid transport by water (Gilley et al, 1987).…”

An optical tachometer for short‐path measurement of flow speeds in shallow overland flows: improved alternative to dye timing

“…Very short travel paths become challenging to time manually, requiring concentration and quick responses, so that flow paths of at least 0·25 m, but up to 6 m, are commonly adopted (Dunne and Dietrich, 1980;Roels, 1984;Abrahams et al, 1986;Govers and Rauws, 1986;Guy et al, 1990;Gilley and Finkner, 1991;Gilley et al, 1992;Beuselinck et al, 1999;Bryan and Brun, 1999;Nearing et al, 1999;Rouhipour et al, 1999). There appears to have been little testing to quantify the precision achieved when timing dye plumes.…”

Effect of mulching techniques on plot scale runoff: FDTF modeling and sensitivity analysis

“…Findeling et al (2003a) have emphasized the impact of a corn residue mulch on evaporation, however they only worked on dry periods without rain. Gilley et al (1991); Yu et al (2000) have developed two models that simulate accurately runoff on a mulch but do not account for infiltration. These models allow the quantification of some specific components of the water balance but do not permit to calculate the global effects of mulching on the whole water balance.…”