Abstract: Zhouqu County is located in the transitional zone from the Qinghai-Tibet Plateau to the Loess Plateau and Sichuan Basin, with a typical alpine valley landform. The territory is characterized by criss-crossing valleys, developed fault zones, and frequent mudslide disasters in mountainous areas, posing a significant threat to human safety and urban construction. In July 2022, a refined risk investigation of geological hazards in Zhouqu County found that there were multiple residual soil sources at the rear edge of the nitrate ditch and a high possibility of mudslides during the flood season. This study takes the debris flow in the nitrate ditch as a representative case, using unmanned aerial vehicles equipped with LiDAR combined with optical photography technology to obtain terrain data of the nitrate ditch. Field surveys and 3D modeling were employed to estimate key parameters such as landslide volume and total debris source material. The FLO-2D software was used to simulate and analyze the entire process of initiation, movement, and accumulation of debris flow in a nitrate ditch under rainfall frequencies of 10%, 5%, 2%, and 1%. followed by hazard zoning evaluation. The results show that the total material source in the nitrate ditch is approximately 9 × 10⁴ m³, which is prone to debris flow disasters under extreme rainstorm conditions. As the frequency of simulated rainfall gradually increases, the scale of debris flows also increases, manifested as the maximum depth, velocity, and range of debris flow accumulation gradually increasing, The debris flow hazard zone is mainly located on both sides of the main channel, branch channel, and mouth road of the nitrate ditch. This study can provide basic information for local debris flow disaster prevention and reduction.