明确不同雨型条件下紫色土坡面产流产沙对水土保持措施的响应特征可为评估紫色土水土保持措施效益提供理论依据。基于紫色土区10个不同水土保持措施径流小区的37场降雨的产流产沙数据,采用K-Means聚类方法,依据平均雨强(I_ave)、最大30 min雨强(I₃₀)、降雨历时(T)、降雨侵蚀力(R_r)指标划分降雨类型,分析不同雨型和水土保持措施对坡面产流产沙的影响。结果表明:①37场降雨可划分为5种雨型,包括Ⅰ型(弱侵蚀、小雨强、长历时)、Ⅱ型(中弱侵蚀、中小雨强、中长历时)、Ⅲ型(中侵蚀、中雨强、中历时)、Ⅳ型(中强侵蚀、中大雨强、中短历时)、Ⅴ型(强侵蚀、大雨强、短历时),其中Ⅲ型为引起坡面水土流失的主要雨型,该雨型导致的产流量和产沙量分别是另外4种雨型的1.2~6.4倍和2.7~19.4倍。②农地窄面埂沟梯地种植和台地种植分别在小雨型(Ⅰ、Ⅱ型)和大雨型(Ⅳ、Ⅴ型)条件下减流效益最佳,主要是由于梯地能有效拦截低雨强、小雨量降雨的径流泥沙,而在大雨量、高雨强的降雨条件下,梯地易蓄满,台地能更有效拦截径流泥沙;其次,林地隔离草带在Ⅰ型降雨条件下的减流效益最佳,主要是由于草带能有效减缓其径流流速,促进下渗和泥沙沉积。研究结果可为进一步明确紫色土区的降雨-水沙关系提供依据。

[Objective] Previous studies in China on slope erosion characteristics under rainfall patterns have primarily focused on the loess region of Northwest China and red soil region of South China. Research on the purple soil region remains limited. Purple soil is the dominant cultivated soil in the Three Gorges Reservoir Region. Following the reservoir’s construction, substantial cultivated land was submerged, compelling local residents to reclaim more steep slopes for cultivation. This has exacerbated soil erosion issues in this region. Considering both rainfall patterns and land characteristics, this study conducted a comparative analysis of runoff and sediment reduction effects under different soil and water conservation (SWC) measures on purple soil slopes in the reservoir area. Understanding the response characteristics of runoff and sediment yield on purple soil slopes to SWC measures under different rainfall patterns could provide theoretical basis for evaluating the effectiveness of SWC measures in purple soil regions. [Methods] Using runoff and sediment yield data from 37 rainfall events across 10 runoff plots under different SWC measures in purple soil regions, rainfall patterns were classified using K-means clustering based on four indicators: average intensity (I_ave), maximum 30-minute intensity (I₃₀), duration (T), and erosivity (R_r). [Results] The results showed that the 37 rainfall events were classified into five patterns: Type I (low erosivity, long intensity, long duration), Type II (medium-low erosivity, medium-low intensity, medium-long duration), Type III (medium erosivity, medium intensity, medium duration), Type IV (medium-high erosivity, medium-high intensity, medium-short duration), and Type V (strong erosivity, high intensity, short duration).. Among these, Type III rainfall was identified as the primary rainfall pattern causing slope soil erosion, with runoff and sediment yields being 1.2-6.4 times and 2.7-19.4 times higher than the other four types. Narrow-terrace cultivation and platform planting exhibited optimal runoff reduction effects under light (Types I-II) and heavy (Types IV-V) rainfall patterns, respectively. [Conclusion] This was primarily because terraces effectively intercepted runoff sediment from low-intensity, small-volume rainfall, whereas under high-volume and high-intensity rainfall, terraces tended to become saturated, and platform fields were more effective in intercepting runoff sediment. Furthermore, the grass strips in forested areas demonstrated optimal runoff reduction effect under Type I rainfall pattern, primarily because the vegetation effectively slowed runoff velocity, enhanced infiltration, and facilitated sediment deposition. These findings provide a basis for further clarifying the relationship between rainfall and runoff sediment in purple soil regions.