Equivalent roughness of gravel-bed rivers
نویسندگان
چکیده
The relation between the equivalent roughness and different grain size percentiles of the sediment in gravel-bed rivers was determined under the hypothesis that the vertical distribution of the flow velocity follows a logarithmic law. A set of 954 data points was selected from rivers with gravel size sediment or larger, with a non-sinuous alignment and free of vegetation or obstacles. According to the results, the ks roughness is equivalent to approximately 2.4D90, 2.8D84, and 6.1D50. No correlation was detected between the sediment sorting and the sediment mobility index on one hand, and, on the other, the coefficient of proportionality of each grain size percentile. CE Database subject headings: Bed roughness; Flow resistance; Gravel; Mountain streams; Fluvial hydraulics. Introduction Let us take a channel formed of granular particles along which there is a turbulent and hydraulically rough flow of a much greater depth than the size of these particles. If it is accepted that the vertical profile of velocity is logarithmic, the channel is wide, 33 / 0 s k z and that 40 . 0 , a Keulegan-type equation can be obtained López, R. and Barragán, J. (2008). “Equivalent Roughness of Gravel-Bed Rivers.” J. Hydraul. Eng., 134(6), 847–851. http://dx.doi.org/10.1061/(ASCE)0733-9429(2008)134:6(847) © 2008 ASCE
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