The impact of near‐surface hydraulic gradients on interrill erosion is still obscure. The objective of this study is to distinguish the dominant interrill erosion process in areas impacted by near‐surface hydraulic gradients. A series of rainfall simulations were conducted on a clay loam soil subjected to near‐surface hydraulic gradients that shifted from drainage/saturation conditions to seepage conditions under three rainfall intensities (30, 60 and 90 mm hr⁻¹) and two slope gradients (5° and 10°). The results showed significant differences in soil loss between all the treatments. The sediment concentrations for seepage conditions were 0.57 to 7.02 times greater than those for drainage conditions. The correlation analysis indicated that the near‐surface hydraulic gradient was a governing factor affecting interrill erosion. The critical flow rate was larger than 90 mm hr⁻¹, suggesting that thin sheet flow does not have sufficient power to detach soil particles without raindrop impact. Furthermore, the detachment rates by raindrop impact were 1.12 to 4.60 times greater for seepage conditions than for drainage conditions. As the near‐surface hydraulic gradient shifted from drainage conditions to seepage conditions, it transitioned from transport‐limited to detachment‐limited, and the contribution of interrill erosion to overall erosion increased from 20.19 to 75.30%. The critical point of dominant interrill erosion process transition existed between saturation (SA) and artesian seepage in 20 cm of hydrostatic pressure head (SP20). The results emphasize the importance of the near‐surface hydraulic gradients’ impact on the interrill erosion process. Further investigations need to be verified in different soil types, steeper slopes and natural storms.

中文翻译：

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近地表水力梯度对钻孔间冲蚀过程的影响

近地表水力梯度对钻孔间侵蚀的影响仍然不明显。这项研究的目的是在受近地表水力梯度影响的地区区分主要的层间侵蚀过程。在经历了近地面水力梯度的粘土壤土上进行了一系列降雨模拟，在三种降雨强度（30、60和90 mm hr ^-1时，排水/饱和条件转变为渗流条件））和两个斜率梯度（5°和10°）。结果表明，所有处理之间的土壤流失存在显着差异。渗流条件下的沉积物浓度是排水条件下的沉积物浓度的0.57至7.02倍。相关分析表明，近地表水力梯度是影响钻头间侵蚀的主导因素。临界流速大于90 mm hr ^-1，表明薄层流没有足够的力量来分离土壤颗粒而不会受到雨滴的影响。此外，在降雨条件下，雨滴撞击引起的脱离速率是排水条件下的1.12至4.60倍。当近地表水力梯度从排水条件转变为渗流条件时，它从运移限制过渡到脱离限制，而层间侵蚀对整体侵蚀的贡献从20.19％增加到75.30％。在20 cm静水压头（SP20）中，主要的层间侵蚀过程过渡的临界点存在于饱和度（SA）和自流渗漏之间。结果强调了近地表水力梯度对钻孔间侵蚀过程的影响的重要性。需要对不同土壤类型的进一步研究进行验证，