Abstract
Mountain river bed is characterized by steep slope, wide range of grain size distribution of bed materials and relatively small water depth to the bed roughness, which cause “stair-like” or “transverse limb” bed form. Flow resistance and bed form with transverse limb are discussed with data observed in a mountain river and obtained by experiments for the bed with sand-gravel mixture or fixed crosspiece roughness. The ratio, λ/Δ, of wave length λ to wave high Δ of limb bed in mountain rivers is about 10, in which case flow resistance is proved to become maximum by experiments. Flow resistance on the bed with relatively large roughness changes largely according to the flow patterns, and it becomes largest when the ratio, hm/Δ, of flow depth hm to the roughness height Δ is about 1.7 for λ/Δ=10
