Abstract
Abstract Few studies focus on the quantitative impact of upslope inflow rate and slope gradient on rill development and erosion processes. Field plot experiments under varying inflow rates (6–36 L min−1m−1) and slope gradients (26, 42 and 57%) were conducted to address this issue. The results showed soil loss rates significantly demonstrated temporal variability in relevance to the rill developing process. Rill erosion and its contribution to soil loss increased with increasing inflow rates and slope gradients by power functions. There was a threshold inflow discharge (12–24 L min−1m−1), under which, rill erosion became the dominant erosion pattern. At the initial stage, downcutting of rill bottom and headward erosion were obvious, whereas rill broadening was significant at the actively rill developing period. Rill density increased with slope gradient increasing from 26% to 42%, and then decreased. For the 57% slope under high inflow rates (24–36 L min−1m−1), gravity caused an increase in the collapse of rills. Mean rill width increased with increasing inflow rates but decreased as slope gradients increased, while mean rill depth increased with increasing inflow rates and slope gradients. Stream power and rill flow velocity were the best hydrodynamic parameter to simulate rill erosion and rill morphology, respectively.
Highlights
Soil erosion is a critical concern for the sustainable development of agricultural regions worldwide (Bennett et al ), and soil erosion could cause non-point source pollution (Wang et al a, b), soil organic carbon loss (Fang et al ), and biodiversity reduction (Li et al )
Under the same inflow discharge condition, the density of rill network increased with slope gradient increasing from 26% to 42%, and decreased with the slope becoming steeper
The results showed soil loss rates significantly related to the fluctuations during the process of rill development
Summary
Soil erosion is a critical concern for the sustainable development of agricultural regions worldwide (Bennett et al ), and soil erosion could cause non-point source pollution (Wang et al a, b), soil organic carbon loss (Fang et al ), and biodiversity reduction (Li et al ). Rill erosion primarily results from concentrated surface flow (Kimaro et al ; He et al ), which is the main source of sediment yield in hillslope erosion processes (Cerdan et al ; Wagenbrenner et al ; Mirzaee & Ghorbani ). Rill erosion occurs when the erosivity of flowing water exceeds a certain threshold of soil resistance; as a result, the micro-terrain of hillslope surface changes and gradually forms a rill (Govers et al ; Knapen et al ; Wang et al ). The evolution of rill networks greatly affects the confluence path of runoff, soil loss, and the micromorphology of the slope surface (Consuelo et al ; Auerswald et al ; Fang et al ; Tian et al ). A further investigation of rill erosion processes on steep hillslopes is urgently needed
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