Effect of rainfall intensity and slope on sediment particle size distribution during erosion using partial eta squared

Abstract

Assessing impacts of different factors on soil erosion is crucial for developing management of watershed resources. The present study aimed at determining the effect of rainfall intensity (RI) and slope steepness (SS) on sediments subjected to raindrop detachment (RD), transport by raindrop splash (ST), raindrop-induced flow transport (RIFT) and transport by flow (FT), using partial eta squared (ɳp2). Experiments were carried out on a plot (6 × 1 × 0.5 m) filled by silty loam soil and subjected to three RIs values of 30, 60 and 90 mm h−1 and three SS values of 5, 15 and 25% in three replicates. The total splash was influenced by RI with respect to ɳp2 and F-value of 0.29 and 14.68. It was found that the particle size <8 μm was significantly (P < 0.001) influenced by SS, while the impact of RI on the particle size >8 μm was more than that of SS. The effect of SS on sediment concentration and particles >63 μm and particle size 2–4, 4–8 and 8–16 μm of sediment reaching the outlet was more than that of RI with respect to ɳp2 of 0.93, 0.58, 0.51, 0.72 and 0.79. However, the clay content (particles <2 μm) with ɳp2 of 0.52 was influenced by RI more than by SS. The runoff rate was also significantly (P < 0.001) influenced by RI (ɳp2 = 0.64). RD-ST and RD-RIFT and RD-FT under different RI and SS combinations indicated that there was a significant difference (P < 0.001) in the transport of detached sediment of different size classes except for RI of 60 mm h−1 and 90 mm h−1 and SS of 25%.