Rainfall Impact Experiments on a Clay Soil Covered by Rock Fragments

The effect of rock cover on rainfall impact and hydrodynamic flow behavior is a topic that needs to be further explored. In this paper, the effects of rock fragments embedded (trapped in the topsoil layer) in clay soil on runoff and sediment yield under simulated rainfall are investigated. The experiments were performed on 0.25 m × 0.25 m sloping microplots with bare soil (control) or a surface covered by 35 embedded rock elements (rock). For each configuration, three rainfall intensities (260.2, 444.0, and 605.2 mm h−1), obtained by Kamphorst’s simulator, were tested, and the whole suspension was collected to determine runoff and sediment yield. The microplots were surveyed before and after the runs to obtain a Digital Elevation Model (DEM) and a DEM of Difference (DoD) and determine sediment yield. The obtained results demonstrated that both runoff and sediment yield (both measured from bowls and calculated from the DoD) increase with increasing rainfall intensity and rock percentage cover. For embedded elements, a higher rate of the sediments moving along the microplots reaches the downstream end of the microplot due to flow channelization. Finally, for the control condition, the erosive phenomena are concentrated under the nozzles, while for the rock configuration, they are also spread in the areas among the rock elements.