Abstract
This study investigated the variation characteristics of micro-topography during successive erosive stages of water erosion: splash erosion (SpE), sheet erosion (ShE), and rill erosion (RE). Micro-topography was quantified using surface elevation change, soil roughness (SR) and multifractal model. Results showed that the area of soil surface elevation decay increased gradually with the development of water erosion. With rainfall, the combined effects of the detachment by raindrop impact and the transport of runoff decreased SR, whereas rill erosion contributed to increase SR. With the increase in slope gradient, soil erosion area gradually decreased at the splash erosion stage. By contrast, soil erosion area initially decreased and then increased at the sheet and rill erosion stages. The width of the Dq spectra (ΔD) values increased at the splash erosion stage and then decreased at the sheet and rill erosion stages on the 10° slope, opposite to that on the 15° slope. The ΔD values decreased with the evolution of water erosive stages on the 20° slope. The slope had an enhancing effect on the evolution of water erosion. In this study, we clarified the essence of micro-topography and laid a theoretical foundation for further understanding diverse hydrological processes.
Highlights
Micro-topography is defined by limited area with fewer changes in the relative elevation
We modeled the micro-topographic changes at different erosive stages with increasing slope gradient (Fig. 1)
This study adopted air-dried soil with a low moisture content, the soil particles swelled with combined rainwater, thereby increasing the soil surface elevation at the splash erosion stage
Summary
Micro-topography is defined by limited area with fewer changes in the relative elevation (usually not more than 5–25 cm). The simple fractal dimension can provide approximate analysis of structured objects, while multifractal analysis (MFA) can effectively analyze spatial heterogeneity inside the structure. It has been widely applied in describing soil surface micro-relief on a micro-topography scale[8,14], as well as geomorphology at basin scale[15]. The object of this study was to investigate variation characteristics of micro-topography in the successive water erosive stages of splash erosion, sheet erosion and rill erosion under simulated rainfall, which would contribute to the understanding of the developmental process of slope erosion and reveal the essence of micro-topography of purple soil on sloping farmland
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