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This article in SSSAJ

  1. Vol. 62 No. 2, p. 430-437
    Received: Dec 10, 1996

    * Corresponding author(s): ywan@hawaii.edu
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Characterizing Interrill Sediment Size by Partitioning Splash and Wash Processes

  1. Y. Wan  and
  2. S. A. El-Swaify
  1. Department of Agronomy and Soil Science, Univ. of Hawaii at Manoa, 1910 East-West Road, Honolulu, HI 96822



Sediment transported from interrill areas is generally finer than the in situ soil matrix. We hypothesized that sediment size depends on the processes dominating interrill sediment transport, i.e., splash or wash, which, in turn, are influenced by rainfall intensity and slope gradient. Aggregate size distribution of directional splash and wash sediment from a Rhodic Eutrustox (Wahiawa silty clay) was measured at 4, 9, 18, 27, and 36% slopes under simulated rainfall with 45, 65, 90, and 135 mm h−1 intensities. Mean sediment geometric mean diameter (GMD) was 0.74 mm for downslope splash, 0.67 mm for lateral splash, 0.59 mm for upslope splash, and 0.40 mm for wash. Both splash and wash preferentially transported aggregates <0.063 mm. However, mean enrichment ratios (ER) for this fraction were <2 for splash and ≈12 for wash. Wash sediment GMD significantly increased with increasing rainfall intensity and slope, and was thus positively correlated with the erosion rate of wash (r = 0.95). In contrast, splash sediment GMD was much less influenced by rainfall intensity and slope, and was weakly correlated with the corresponding splash rate (r = −0.17 for total splash). Splash tended to generate sediment with similar size to the in situ soil and the size sorting process was in a matrix-limited regime. Wash appeared to be in a force-limited regime and produced sediment that was much finer than the in situ soil.

Research supported by USDA Section 406, Grant Agreement no. 91-34135-6177.

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