极端降雨对晋西黄土区农地流域泥沙连通性的影响

目的]研究极端降雨事件对小流域坡沟系统泥沙连通性的影响，进而为流域综合治理与灾后重建提供理论依据。方法]以地处黄土残塬区的晋西吉县蔡家川农地小流域为研究区，采用无人机与遥感影像对2021年10月山西极端降雨事件前后坡沟系统进行航测与实地调查，分析极端降雨前后的景观格局变化，量化坡沟系统泥沙连通性，识别滑坡点位空间分布与地形特征，评价流域内典型工程措施对极端降雨的响应。结果]农地流域此次降雨历时84 h,累计降雨量160.4 mm,降雨强度1.9 mm/h,降雨频率0.16%,为百年一遇的极端暴雨。暴雨后流域斑块数量增加，景观形状指数增大，蔓延度指数减小，香农多样性指数减小。暴雨前流域内泥沙连通性分布不均，暴雨后泥沙连通性增大。暴雨后滑坡位点泥沙连通性减小，滑坡多发生在0°～10°和40°～50°的条件下，所占比例分别为29.11%和17.74%。结论]极端暴雨事件诱发的滑坡影响了泥沙连通性，根据泥沙连通性空间变化可识别水土流失位点，能够用于评估典型水土保持工程措施对极端降雨的响应，研究结果可为流域综合治理及极端降雨事件发生后开展生态恢复提供支撑。

Effects of Extreme Rainfall on Sediment Connectivity in a Farmland Watershed of the Gully Region in the Western Shanxi Province of the Loess Plateau

Objective] The aims of this study focus on the influence of extreme rainfall events on sediment connectivity of slope-gully system in small watershed, and further provide theoretical basis for comprehensive watershed management. Methods] The farmland watershed in Caijiachuan watershed in Ji County of the Loess Plateau was taken as the research area. UAV and remote sensing images were used to carry out aerial survey and field survey on slope and gully system before and after the extreme rainfall event in Shanxi in October 2021. The landscape pattern changes before and after extreme rainstorm were analyzed, the sediment connectivity of slope-gully system was quantified, and the spatial distribution and topographic features of landslide points were identified, the responses of typical engineering measures to extreme rainfall were evaluated. Results] The rainfall event lasted for 84 hours, with a cumulative rainfall of 160.4 mm, a rainfall intensity of 1.9 mm/h and a rainfall frequency of 0.16%. It was an extreme rainstorm that occurred once in a hundred years. After the rainstorm, the number of patches increased, the landscape shape index increased, the Contag index decreased, and the Shannon diversity index decreased. Sediment connectivity unevenly distributed in the watershed before the rainstorm, but it increased after the rainstorm. After the rainstorm, the sediment connectivity of landslide site decreased, and the landslide mainly occurred on the slopes with 0°～10° and 40°～50°, accounting for 29.11% and 17.74%, respectively. Conclusion] Landslides induced by extreme rainfall events affect sediment connectivity, and the sediment connectivity index can be used to identify landslides sites thus can be used to assess the response of typical soil and water conservation engineering measures to extreme rainfall. The results of this study can provide support for integrated watershed management and ecological restoration after extreme precipitation events.