Resistance to flow because of the presence of bed forms over armored river beds is of paramount importance, leading to the effective design of water-resources-related projects. Based on the findings over bed armored surfaces, it is shown that the controlling roughness ( ) can be taken as ks equal to the median diameter of the armor layer. Analytical methodologies for total and grain friction factors have been proposed here which take flow non-uniformity into account using the velocity distribution and friction slope. The percentage composition of form friction factor in the total friction factor was estimated to be 40%. The results were explained in light of the coupling of the sediment threshold problem with the friction factor and coarse-grain rearrangement in armor layer. The computed form friction factor by proposed method was compared with Keulegan’s method and is found to give satisfactory results, showing 80% agreement of all field data sets.
