Transport of a Noncohesive Sandy Mixture in Rainfall and Runoff Experiments

Abstract

Abstract Rainfall intensities of 45, 100, and 150 mm/hr with systematically varied kinetic energies were applied to a saturated noncohesive, sandy bed 3 m long and set at slopes of 0.5 and 5%. Detailed size analyses of solids discharged showed that the <31‐µm fraction was most readily mobilized and behaved as a suspended load; the 31‐ to 250‐µm fraction was transported slowly, much apparently as saltating bed load; the 0.25‐ to 4‐mm fraction was transported rapidly, grains tending to move as rolling bed load; the >4‐mm fraction behaved as a lag gravel. The sedimentary properties of bed deposits also reflected the differentiation of various size fractions and minerals in the original mixture. The effects of raindrop impacts within the flow were more important in promoting transport of solids than the aerial component of splash. Under conditions where overland flow had developed, transport of solids was related directly to rainfall intensity and variations in rainfall energy that were associated with variations in raindrop impact frequency. Increases in rainfall energy due to increasing raindrop sizes did not result in increases in solids discharged.