Granite hilly areas are among the most ecologically fragile zones in China, and are susceptible to backward erosion under conditions of prolonged heavy rainfall and steep slopes. However, the spatiotemporal dynamics governing sediment generation and energy dissipation during gully headcut erosion in hilly granite areas remain unclear. In this study, through a field in situ scouring test, we investigated the temporal and spatial variation rules of gully headcut erosion energy consumption, sand production characteristics and sediment sorting characteristics of different soil layers (the laterite and sandy layer) at different headcut heights (25, 50, 75, 100 and 125 cm). The results showed that the energy consumption in the sandy layer exceeded that in the laterite layer, and the energy consumption in the upstream area (UA), gully head (GH), and gully bed (GB) consistently and linearly increased with experiment duration (R=0.765–0.999, <0.01). Moreover, the energy consumption in the GH () and the energy consumption in the GB () increased with the headcut height and discharge rate, whereas the energy consumption in the UA () was predominantly influenced by the discharge rate. The GH contribution exceeded 50.00 % when the headcut height was greater than 100 cm; this height was the critical drop height for causing a sudden change in the gully headcut erosion. The sand production rate (S) reached its maximum value within 10 min of runoff initiation. Additionally, S initially decreased and then stabilized as a power function of the test duration, and S was greater in the sandy layer than in the laterite layer. In the runoff scouring process, the soil loss (S) was concentrated in the UA and GH, while S was low in the GB. The total of soil loss amount (S) and the soil loss amount of the GH (S) linearly increased (<0.01) with increasing total energy consumption () and , indicating that energy consumption can be considered to assess the retroactive erosion. Significant differences in the sediment content and enrichment rate between the laterite and sandy layers occurred, and the 1–2 mm particles accounted for the greatest proportion of sediments in both layers. The fine particles exhibited an enrichment trend, resulting in coarser slope particles. At the later scouring stages, coarse particles exhibited reduced cohesion and were susceptible to transport, this contributed to a gradual increase in coarse particles. This study could provide a theoretical basis for the systematic prevention and control of traceable granite erosion.

中文翻译：

---

华南花岗岩丘陵区不同切头高度对切头侵蚀及产沙过程的影响


花岗岩丘陵地区是我国生态最脆弱的地区之一，在长期强降雨和陡坡条件下容易遭受后向侵蚀。然而，丘陵花岗岩地区沟壑侵蚀过程中控制沉积物生成和能量耗散的时空动力学仍不清楚。本研究通过现场原位冲刷试验，研究了不同土层（红土层和砂层）不同切头高度下沟道切头侵蚀能量消耗、产沙特征和泥沙分选特征的时空变化规律。 25、50、75、100 和 125 厘米）。结果表明，砂层能耗超过红土层，且上游区（UA）、沟头（GH）和沟床（GB）能耗随实验时间持续线性增加（ R=0.765–0.999，<0.01）。此外，GH（）中的能量消耗和GB（）中的能量消耗随着切头高度和排出速率的增加而增加，而UA（）中的能量消耗主要受排出速率的影响。当切头高度大于100 cm时，GH贡献超过50.00%；该高度是引起沟壑切头侵蚀突变的临界落差高度。产砂率 (S) 在径流开始后 10 分钟内达到最大值。此外，S 作为测试持续时间的幂函数先下降然后稳定，并且沙层中的 S 大于红土层中的 S。径流冲刷过程中，土壤流失量（S）集中在UA和GH区域，而GB区域土壤流失量较低。 土壤流失量总量（S）和GH土壤流失量（S）随着能源消耗总量（）和 的增加而线性增加（<0.01），表明可以考虑能源消耗来评估追溯侵蚀。红土层和砂层沉积物含量和富集率存在显着差异，两层沉积物中1~2 mm颗粒所占比例最大。细颗粒呈现富集趋势，导致坡度颗粒较粗。在冲刷后期，粗颗粒的内聚力降低，易于输送，导致粗颗粒逐渐增加。该研究可为可追溯花岗岩侵蚀的系统防治提供理论依据。