Size Distribution and Wet Density of Sediment Eroded Under Simulated Rainfall

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Abstract
Masa soil and Red-Yellow soil were compared in terms of the size distribution of the sediment (primary particles plus aggregates) eroded under simulated rainfall and of the wet density of the >210 μm sediment that exists during the transport by surface flow. The sediment-size distribution for the Masa soil, which is generally coarse-textured and lacks cohesion, was monomodal showing a peak in the size range of 5–20 μm, and the eroded sediment consisted of both primary particles and aggregates. On the other hand, the largest peak in the sediment-size distribution for the Red-Yellow soil, which shows a relatively fine texture and high stability of aggregates, corresponded to the 210–2,000 μm size range irrespective of the monomodal or bimodal distribution. The sediment eroded from the Red-Yellow soil consisted mostly of aggregates. The wet sediment density was significantly higher for the >210 μm sediment from the Masa soil than for the >210 μm sediment from the Red-Yellow soil. This difference in wet sediment density may account for the difference in the transportability between the two sediments.