###### Abstract  
Dashing Gully, located in Miyun District, Beijing, exhibits a high susceptibility to debris flow due to its unique geological and topographical characteristics. The area is characterized by well-developed rock joints and fissures, intense weathering, a steep gradient, and a constricted gully morphology. These factors contribute to the accumulation of surface water and loose sediment, significantly increasing the risk of debris flow events. Following a comprehensive field geological investigation of Dashing Gully, key parameters for simulation were obtained, including fluid weight, volume concentration, and rainfall. The formation and development conditions of potential mudslides were analyzed, and numerical simulations were conducted using FLO-2D software (version 2009) to assess scenarios with rainfall probabilities of 1 in 30, 50, and 100 years. The simulations accurately reconstructed the movement velocity, deposition depth, and other critical movement characteristics of mudslides under each rainfall scenario. Using ArcGIS, pre- and post-treatment hazard zoning maps were generated for Dashing Gully. Furthermore, the efficacy of implementing a retaining wall as a mitigation measure was evaluated through additional numerical simulations. The results indicated that mudslide velocities ranged from 0 to 3 m/s, with deposition depths primarily between 0 and 3 m. The maximum recorded velocity reached 3.5 m/s, corresponding to a peak deposition depth of 4.31 m. Following the implementation of the retaining wall, the maximum deposition depth significantly decreased to 1.9 m, and high-risk zones were eliminated, demonstrating the intervention's effectiveness. This study provides a rigorous evaluation of mudslide movement characteristics and the impact of mitigation measures within Dashing Gully. The findings offer valuable insights and serve as a reference for forecasting and mitigating similar mudslide events triggered by heavy rainfall in gully mudslides. mudslide; numerical modelling; FLO-2D; hazard; geohazard control +
Footnote †: journal: Medical  
Debris flows are complex two-phase flows composed of solid and liquid phases, with their movement mechanisms governed by the properties of each phase and their interactions [2]. Dynamics characteristics can vary significantly at different locations within a mudslide [3]. Numerical simulation methods enable the visualization of mudslide movement, providing data on parameters such as velocity, deposition depth, and other relevant attributes. This information is crucial for evaluating the effectiveness of mudslide mitigation strategies. In recent years, extensive research on mudslides has been conducted by scholars worldwide. With the rapid advancements in science and technology during the 21 st century, various software tools capable of simulating mudslide dynamics have emerged, including Geoflow, Massflow-2D [4], RAMMS [3], FIO-2D [5], and CFX. Numerous researchers have utilized ArcGIS [6; 7; 8] to visualize numerical simulation results, effectively illustrating the dynamics of mudslide events. These visualizations provide a valuable reference for developing mudslide prevention and control strategies. Furthermore, understanding mudslides and mass movements has broader implications, extending to marine environments and the geological record of sediment transport on land and in the oceans [9; 10]. This knowledge is relevant for modeling marine instability and landslide processes as well [11; 12; 13; 14]. Several studies have employed numerical simulations to investigate mudslides. [PERSON] et al. [15] simulated the movement of debris flow beneath Stoze, Slovenia. [PERSON] et al. [5] compared the performance of two numerical software packages, FLO-2D and Debris-2D, for debris flow modeling. [PERSON] et al. [16] used FLO-2D to establish a mathematical model of the Umyeon Mountain debris flow. [PERSON] [17] assessed the effectiveness of debris flow mitigation measures using the Kanako 2D software (Ver.2.00). [PERSON] et al.