The laboratory experiments on sediment transport conducted by G. K. Gilbert differed importantly in technique from such studies of more recent date. Gilbert’s flume was level and could not be altered in slope. Sediment was introduced at the upper end at a predetermined rate and by deposition built a bed gradient sufficient to transport the introduced load. The adjustment of slope in Gilbert’s flume has contributed to the idea widely held by geologists that a river achieves equilibrium by adjusting its slope to provide just the velocity required for the transportation of the supplied load.
In fact, slope adjusts but little to a change in amount of introduced sediment load. The adjustment takes place principally among other hydraulic factors: width, depth, velocity, bed forms, channel pattern, and pool-riffle sequence. Gilbert sensed this complicated adjustment process, but its details are as yet only partially known in quantitative terms.