| Landslides are significant geohazards that threaten transportation infrastructure and public safety,
particularly in rural areas such as southeastern Idaho. Beyond endangering lives, these slope
instabilities disrupt access to essential services and impose substantial financial burdens on the
state. This study investigated two active landslide sites in southeastern Idaho through repeat
Unmanned Aircraft Systems (UAS) surveys conducted between July 19, 2023, and October 3,
2024. The UAS platforms were equipped with LiDAR and photogrammetry sensors to generate
high-resolution point cloud data. Multiple change detection techniques—including point cloud-topoint cloud (C2C) comparison, DEM of Difference (DoD), cloud-to-mesh (C2M) analysis, and
Multiscale Model-to-Model Cloud Comparison (M3C2)—were employed to quantify surface
displacement and monitor slope dynamics. Results from these analyses were compared with insitu inclinometer measurements obtained during the same period. During the study period, a
mudflow occurred along US Route 26, near Swan Valley, Idaho. The UAS surveys indicated a
material loss of up to 2.6 m and an accumulation at the toe of the slope of up to 2.3 m. Inclinometer
readings from nearby instruments did not register any subsurface deformation, as they were
installed near the site but outside the core movement area. For the second study site near Wayan
Idaho, the M3C2 analysis detected material movement of up to 0.7 m in an isolated location below
the highway along Tincup Creek. This integrated approach demonstrates the effectiveness of UASbased remote sensing in monitoring landslide activity and provides valuable insights for hazard
assessment and mitigation planning.
Keywords: Inclinometer, Landslides, LiDAR, M3C2 Analysis, Point cloud, UAS |