Changes in bed condition, flow resistance and sediment transport are discussed in gravel-cobble covered bed where sand is supplied artificially like as river reaches downstream of dam reservoirs, on the basis of experimental results obtained in a large scale flume called "the experimental river" in the Aqua Restoration Research Center, PWRI. Variations of the bed condition were clarified minutely by the use of a sophisticated system that enables automatic measurement of 1cm mesh intervals even under flowing conditions. Flow resistance and non-equilibrium process of sediment transport are confirmed to correspond closely to bed states under subcritical condition.
