Application of UAV images to rockfall investigation at the high and steep slope

Due to the limit of complex terrain，the rockfall investigation is difficult to conduct at the high and steep slope，which is always one of the issues to obtain geological hazard information quickly and accurately in geological hazard investigation. In past studies，the application of UAV remote sensing technology was reported in loess，plateau and other areas，but the study of the rockfall investigation had not been reported on high and steep slope in Southwest China yet. This paper takes the Chuxianchang slope rockfall disaster area of the Jinping II Hydropower Station as an example，applying unmanned aerial vehicle (UAV) photogrammetric technology to the rockfall investigation on the high and steep slopes. The high resolution remote sensing images were obtained by UAV oblique photogrammetry，three-dimensional (3D) modeling of remote sensing image and remote sensing interpretation of geological disaster was performed. It summarized the technical flow of UAV remote sensing system for rockfall investigation in high and steep slope. By a 3D real-scene model，it accurately analysed the space distribution，instability mode and evolution process of rockfall disaster，and investigated the distribution characteristic of instable rockfalls in the area. Based on the 3D point cloud model，it accurately extracted the attribute information of geological disaster body，the measured rockfall volume is 11.7 m3. By the plane fitting based on the least square method，the obtained rockfall occurrences of two main structural planes are 275.4°∠31.2° and 103.5°∠63.3°. The practice results show that UAV remote sensing technology has obvious feasibility and superiority in the rockfall disaster investigation of the high and steep slope，it can be applied to the rockfall investigation in the high and steep slope.