Media reports indicated that the National Audit Office believed that drones were not being used effectively in most landslide dam monitoring operations. In response, the Forestry and Nature Conservation Agency (FANCA) explained that the National Audit Office reviewed the emergency investigations of five landslide dams conducted by the FANCA in 2025 and 2026 and found that drones were only used at one dam to confirm the latest overflow status. This was not conducive to monitoring changes in water levels and overflow conditions of landslide dams. The purpose of the National Audit Office’s review was to remind the FANCA to make better use of drones to keep abreast of the latest overflow situation.While drones can provide high-resolution imagery, their current application in monitoring landslide dam overflows remains constrained by various environmental and technical limitations. Drone range is restricted by battery capacity. Furthermore, as drones rely on radio frequency (RF) controls, their operations are strictly limited to daylight hours and favorable weather devoid of wind, rain, or dense cloud cover; consequently, not all locations and timeframes meet the conditions for drone operations. Given that some landslide dams are situated in remote, steep valleys with limited signal coverage, these combined environmental and technical constraints explain why drone aerial surveys were successfully executed at only a single location during the active overflow events of multiple landslide dams. Therefore, during the emergency investigation phase of the landslide dams, the FANCA comprehensively utilized technologies and equipment such as drone aerial photography, airborne remote sensing imagery, satellite imagery, and on-site or remote cameras, based on the location and conditions of the landslide dams, to monitor the changes of these landslide dams in real time. In addition, water level gauges, rain gauges, and micro-seismometers were installed in the landslide dams to establish a comprehensive monitoring and early warning network in order to keep abreast of the overflow time or various abnormal conditions. Regarding the five landslide dams mentioned in the audit report, the FANCA used drones for monitoring whenever possible. Among them, the landslide dams of Taigang River in Hsinchu and Mugua River in Hualien have low water storage capacities, which means that there was a low level of threat to the downstream areas in the event of a breaching. Therefore, drones are used to take aerial photos periodically, while webcams are installed on site for real-time monitoring. During the period when landslide dams formed at Matai’an River, Wanli River, and Liwu River in Hualien, drones were used intensively for daily monitoring of the landslide dams.
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