Movement of solids in air and water by raindrop impact. effects of drop-size and water-depth variations

摘要: Transportation of 200 pm sand grains by impacting raindrops in both air and water was experimentally investigated through the depth range 0-75 mm, employing four drop sizes. Airsplash movement, greatest for large drops bare sand, fell rapidly with decreasing dropsize increasing depth. Shallow surface inhibited airsplash strongly, yields falling factors 0-2 mm. Hence, airsplashing solids, even if randomly directed from any one point, must produce net migration to water-covered surfaces. Drops over about 1.5 mm diameter disrupt on at terminal velocity, generating disturbances which can, is shallow, suspend soil particles. Smaller evidently penetrate surfaces without disruption, disturbing particles more directly efficiently. If target flows, very slowly low slopes, downstream particle (rain-flow transportation) results. Rain-flow transportation rates rose zero near-maximum values 2 Actual maxima were reached depths 2-3 diameters, transport declining further increases. The combination rain-flow extends areas where overland flow either absent or too weak, acting alone, move solids significantly.