Ephemeral gullies (EGs) play a crucial role in hydrological connectivity, soil erosion, and land degradation. However, little research has focused on flow hydraulics in concentrated flow channels and their effects on EG erosion on steep loessial slopes. A simulated experiment of rainfall (60–120 mm hr⁻¹) and upslope inflow (0.45–2.25 m² hr⁻¹) were conducted on concentrated flow channels with loess at 15°–25° slope gradients. The concentrated flow was turbulent and subcritical in most cases. The flow shear stress, stream power, and unit stream power in the concentrated flow channels varied from 32.65 to 109.40 N m⁻², 10.85 to 38.66 N m⁻¹ s⁻¹, and 0.08 to 0.16 m s⁻¹, respectively. The EG depth, width, and width-depth ratio varied within 14.8–24.6 cm, 18.5–33.8 cm, and 1.13–1.83, respectively. Moreover, the EG depth and width increased in a power function with the runoff rate (R² = 0.82–0.83; p < 0.01). The sediment yield rate (Ys) varied within 15.94–94.44 g m⁻² s⁻¹ under the different treatments and had a good linear relationship with the runoff rate (R² = 0.78; p < 0.01). Furthermore, the flow shear stress and stream power can be used to predict Ys by linear functions. The critical runoff rate and shear stress to initiate EG erosion were determined to be 0.09 m³ hr⁻¹ and 2.66 N m⁻². However, the coefficient of determination for the linear relationship between Ys and shear stress was low (0.58). The results indicate that the flow shear stress mechanism might not be enough to explain sediment load variation for EG erosion, and headcut erosion mechanism should be taken into account.

中文翻译：

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陡峭黄土斜坡上降雨和上坡流入引起的集中流道中的短暂冲沟侵蚀

临时沟壑 (EG) 在水文连通性、土壤侵蚀和土地退化方面发挥着至关重要的作用。然而，很少有研究关注集中流道中的流动水力学及其对陡峭黄土斜坡上 EG 侵蚀的影响。降雨（60-120 mm hr ^-1）和上坡流入（0.45-2.25 m ²  hr ^-1）的模拟实验在15°-25°坡度的黄土集中流道上进行。在大多数情况下，浓缩流是湍流和亚临界的。集中流道中的流剪应力、流功率和单位流功率从32.65到109.40 N m ^-2、10.85到38.66 N m ^-1  s ^-1和0.08到0.16 m s ^{-1 变化}， 分别。EG 深度、宽度和宽深比分别在 14.8-24.6 cm、18.5-33.8 cm 和 1.13-1.83 内变化。此外，EG 深度和宽度随径流速率呈幂函数增加（R ²  = 0.82–0.83；p  < 0.01）。不同处理下的沉积物产率（Ys）在15.94-94.44 g m ^-2  s ^{-1 之间}变化，并且与径流速率具有良好的线性关系（R ²  = 0.78；p  < 0.01）。此外，流动剪切应力和流功率可用于通过线性函数预测 Ys。启动 EG 侵蚀的临界径流速率和剪切应力被确定为 0.09 m ³  hr ^-1和2.66 N m ^-2。然而，Ys 和剪切应力之间线性关系的决定系数很低 (0.58)。结果表明，流剪应力机制可能不足以解释EG侵蚀的泥沙负荷变化，应考虑切头侵蚀机制。