The catastrophic debris flow in the Qinling Mountains of Xi’an, Shaanxi province, China, from 11 August 2023

Neglecting terrain-induced channel aggradation can lead to severe consequences, including greater economic losses and higher casualties. On 11 August 2023, a catastrophic channelized debris flow triggered by short-duration intense rainfall in Jiwozi village near Xi’an City, Shaanxi Province, China, destroying three buildings and resulting in 24 fatalities, with three people missing. This study investigates the kinematic process and underlying mechanisms of the debris flow using field investigations, terrain analysis, and numerical simulations. The rain-flood method and Rapid Mass Movement Simulation (RAMMS) software were employed to simulate the propagation process of the debris flow across 20-year, 50-year and 100-year recurrence intervals. The impact of basal friction and erosion parameters on simulation accuracy were examined based on trial-and-error approaches. The optimal parameter combinations were confirmed by comparing simulated boundaries with observed data. At two potential channel blockage sites, simultaneous increases in flow height and rapid decreases in velocity were observed. A two-factor model combining maximum flow height and velocity was utilized to construct hazard zoning. This study underscores the critical influence of local terrain on the propagation and mobility of channelized debris flow during heavy rainfall.忽视地形诱导的河道淤积（terrain-induced channel aggradation）可能引发极为严重的后果，包括巨额经济损失与大量人员伤亡。2023年8月11日，中国陕西省西安市（Xi’an City）近郊的箕窝子村（Jiwozi Village）发生由短时强降雨触发的特大型沟道泥石流灾害，该灾害损毁3处建筑，造成24人死亡、3人失踪。本研究通过野外调查、地形分析与数值模拟手段，探究了此次沟道泥石流的运动过程与内在致灾机理。研究采用雨洪法与快速块体运动模拟（Rapid Mass Movement Simulation，RAMMS）软件，针对20年、50年、100年一遇的重现期，模拟了该泥石流的运动演进过程。本研究通过试错法，分析了底面摩擦与侵蚀参数对模拟精度的影响规律。通过将模拟得到的泥石流运动边界与实地观测数据进行比对，确定了最优参数组合。在两处潜在的沟道堵点处，观测到流体高度同步抬升且流速骤降的现象。本研究构建了融合最大流体高度与流速的双因子模型，用于开展泥石流危险性区划。本研究凸显了局地地形对强降雨条件下沟道泥石流运动传播与运动活动性的关键影响。