Landslide dam breaking can be a severe threat to the downstream area because of the damage caused by massive debris flow as a secondary disaster. A magnitude 6.3 earthquake struck Taiwan on June 2, 2013, and triggered
a landslide, which resulted in the formation of a natural landslide dam in the South Qingshuigou watershed near
the Phoenix Valley Bird Park. To efficiently estimate the landslide’s scale and evaluate the landslide dam’s stability,this study used an unmanned aerial vehicle to photograph the landslide scene and employed image-based modeling (IBM) approaches to construct a three-dimensional (3D) model of the landslide scene. This study also performed coordinate transformation using length constraints to obtain a 3D model at an absolute scale. The dimensionless blockage index (DBI) could be calculated for the landslide dam by using spatial information retrieved from the constructed 3D model. The volume of this earthwork was estimated as 136,588 m3, and the DBI of the landslide dam was 3.37, indicating that the landslide dam was unstable. The constructed model provides timely and precise 3D geoinformation and can be used as a reference for aftermath strategizing.
Key Words: UAV, IBM, 3D model, dimensionless blockage index.