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A laboratory study is conducted to measure Darcy-Weisbach roughness coefficients for selected gravel and cobble materials. Varying rates of flow are introduced into a flume in which a given size class of gravel or cobble material is securely attached. Roughness coefficients are calculated from measurements of discharge rate and flow velocity. The laboratory data are used to develop regression equations for relating roughness coefficients to surface cover and Reynolds number. Accurate prediction of roughness coefficients for gravel and cobble surfaces will improve our ability to understand and properly model upland flow hydraulics.