## 2 Materials and Methods
### Study Area Overview  
The study area is located at the Luijiawan resettlement site in Dayao County, Yunnan Province, within a tectonically incised mid-mountain belt along the Jinsha River. The terrain exhibits a southeast-to-northwest decline in relief, with a highly dissected landscape. Ridge lines predominantly trend north-south, aligning with regional master faults. The landform is characterized by deeply incised mid-mountain terrain, with a maximum relative relief of 901.92 m, resulting in the development of pronounced steep slopes. Data acquisition was based on the China Geodetic Coordinate System 2000 (CGCS2000) for planar coordinates, the 1985 National Elevation Datum, and the 3\({}^{\circ}\) Gauss-Kruger projection with a central meridian of 102\({}^{\circ}\) E. Terrain mapping was carried out using a DJI Matrice 350 RTK UAV equipped with a Zenmuse L2 airborne LiDAR sensor. The LiDAR sensor is equipped with multi-frequency scanning and dual-polarized antennas, achieving a ranging accuracy of 2 cm at a distance of 150 m and a maximum range of 500 m. Each laser pulse can record up to five returns, with a scanning field of view of \(\pm\)30\({}^{\circ}\) in the vertical direction and \(\pm\)45\({}^{\circ}\) in the horizontal direction, enabling vegetation penetration to accurately capture the ground surface. Flight paths were designed in a grid pattern, with a consistent flight altitude of 70 m above ground level. The flight lines were further refined to account for substantial elevation changes and steep terrain, ensuring full coverage of critical and potentially occluded areas. Figure 1 presents a panoramic view of the Luijiawan resettlement site.  
The site is located in a transitional zone where the first terrace of the Jinsha River merges with a debris-flow fan and colluvial deposits. The cross-section exhibits a break-line morphology, characterized by a southeast-facing cliff locally exceeding 70\({}^{\circ}\) in slope and rising over 500 m in height. In contrast, the northwest side consists of a gently inclined residential platform formed through artificial leveling. The area displays a compound hazard geomorphology, characterized by potential gravitational disasters--such as landslides, rockfalls, and debris flows--that are spatially complex and highly abrupt. The stratigraphy is primarily composed of Holocene debris-flow deposits (Q\({}_{4}\)set), alluvial-pluvial deposits (Q\({}_{4}\)al+pl), and colluvial deposits (Q\({}_{4}\)col) from the Quaternary, along with the Middle Jurassic Shedian Formation (J\({}_{2}\)s). The unconsolidated deposits consist of grav  
Figure 1: Overview of the Lu jia wan Resettlement Site.  
els, angular clasts, and weathered sandstone fragments, forming loose and heterogeneous masses that serve as the primary material basis for unstable accumulations. In contrast, the Shedian Formation--characterized by thick-bedded massive quartz sandstone with mudstone interbeds--provides a rigid structural framework that controls the development and configuration of hazardous rock masses. High-resolution terrain data acquired via airborne LiDAR are used to generate a realistic three-dimensional surface model (with a resolution of 0.05 m), which serves as the terrain input for RAMMS:ROCKFALL simulations. Based on engineering investigation results, the spatial distribution of hazardous rock masses is illustrated in Figure 2.  
In summary, the Lujiawan site integrates complex geomorphic structures, fragmented deposits, and multiple geological hazards, making it a representative location for the identification of unstable steep-slope rock masses and the analysis of rockfall dynamics.